In it's class the SL90 delivers, but you could quickly outgrow it.
Positive Product Points
Makes better espresso than you'll get at many "coffee bars" if you use the non-pressurized filters. Love the see-thru water reservoir that makes it so easy to see when you need to refill. Great steaming capability that allowed me to quickly get up to speed on frothing. Makes excellent Americanos and fairly decent espresso if you get everything right (tamp, grind, non-press filter, etc).
Negative Product Points
If you need to make multiple (more than two) sequential drinks, it's not that much fun to use. Very succeptible to internal disconnect of the hoses and some electrical plugs during shipment.
First, some comments about product concerns or improvements. The drip tray needs to be deeper because it has to be drained fairly often. The built-in tamper is mainly useful while you are learning "and" using the included pressurized filters. Once you've built some skills, both the built-in tamper and pressurized filters are never used. The pump in the SL90 is not strong enough to deliver more than 3.5ozs of water in 25 seconds. This basically prevents you from making Cafe Cremas with this machine which require 5ozs of water in 25 seconds.
Solis should have put a horizontal bar across the front of the top (cup storage area). The cups have a tendency to slide off the front, especially when you lift the plastic water reservoir for filling. There's a plastic nib on the top of the reservoir that will catch the back middle cup and flip it if you're not careful to pull the cups forward. The preprogrammed buttons will be of use for the first couple of weeks and then useless thereafter because you'll progress to either timing or visually ending your shots. I wish Solis had used the standard 58mm portafilter because it holds more coffee.
I was not impressed when I received the SL90 and found it had two problems right out of the box. A water line had come loose which I repaired myself. Wasn't too impressed with the way Solis holds plastic tubing onto the water fittings (they use tie wraps which seemed a little cheesy to me). The unit would not pump water either which was a disconnected plug on the control board. My impression is that Solis should either employ better connections for hoses and plugs, better packing or both.
On the up-side, the price is right and the unit is easy to use. I've only been making espresso for a month and can already surpass local coffee-houses. Your first purchase (along with the SL90) should be the non-pressurized double filter. This is essential to getting the best espresso possible from your SL90. I've found that the easiest way to load the double non-pressurized filter is to slightly overfill it, wipe the excess with a finger and then tamp. This is about 15-16grams of coffee which is slightly more than the recommended 14grams for a double. Also, get a good "metal" 53mm tamper to do your packing which is essential to being able to take advantage of the non-pressurized filter.
I've done back-to-back drinks (more than two), and this unit will do it, but boiler temp starts to fall off after the first two drinks. If you only need to prepare one or two drinks at a time, the SL90 is a very fine solution. If you need to do more than that, I'd recommend getting a higher-end HX machine and skip the SL90. I've only had the product for a month, make espressos every day and am already wishing I'd spend the extra bucks for an HX class machine.
The steaming capability is really the strong suit of the SL90. This baby will definitely get the job done and quickly. You can create loads of microfoam, latte milk, etc and the learning curve isn't very steep. The SL90 will make very good milk-based espresso drinks that will impress your friends and family. That part is very fun to do and I enjoy seeing people's faces when they taste cappas, mochas, etc.
All in all, the product delivers good espresso and in its price range the SL90 is a very reasonable investment.
Bought my unit directly from Baratza under their "refurbished" offering. The folks at Baratza are very helpful. The unit arrived with the water hose disconnected and an electrical plug popped loose. These are common problems that seem to be normal with the SL90, but are easily repaired if you are handy and willing. Baratza will walk you through this stuff over the phone and they offer great service.
Three Month Followup
I'm a little over 4 months into use of the product and have learned to use it quite well. Here's my updated thoughts on the SL90:
Overall: For the price point of this machine, it's really a fantastic product. This is because with proper skills, grinder, coffee quality, etc, you can turn out some truly killer shots. Consistency is a bit of a challenge, but 8 of 10 times I can make very good espresso with the other two still being acceptable. If you read enough on CoffeeGeek, you'll find that lots of people can make great shots on SL90's and Silvia's that aren't tons better when they upgrade to more expensive machines. There are good reasons to upgrade from the SL90, but flavor improvement doesn't necessarily have to be one of them.
Dependability: After the initial problems I had when it was out-of-box, there have been no major problems. I currently have one small problem where the Steam/Water knob doesn't activate the pump about half the time and I have to close/reopen it to make it work. Have tried a few suggestions from Baratza, but still have the problem. (Update Feb 2004 - Baratza sent me a new microswitch and that solved the problem).
Weight/sturdiness: The SL90 is too light when the water tank is less than 1/3 full. Pulling on the portafilter to tighten it will often result in jerking the whole unit sideways. You'll see a lot of people talk about cabinet flex with the SL90. Actually, the flex doesn't really affect anything, but the light weight does and Solis should add weight to hold the unit still.
Using the non-pressurized (NP) filter baskets: I've found what I believe to be the "secret sauce" for both the single and double (optional) NP filter baskets (assuming you've developed some skill, have fresh beans and an adequate grinder). With the single NP basket, use 11gms of coffee with a normal 20-30lb tamp. For the double NP basket, use 17-18gms of coffee which will overfill the basket. But you can accomplish all 17-18gms by filling the basket, tap it on the counter to settle the coffee, then fill with the remainder, level and tamp.
It takes adequate amounts of coffee to get great results from the SL90 53mm baskets and these amounts will do the job nicely. You'll note that with the PF locked and loaded, the tamped grounds are actually touching the screen in the brew-head, but this is OK and causes no problem. Actually, these amounts are a good way to have pretty dry pucks versus the soupy ones you will get with smaller/standard amounts of coffee. It probably goes against the grain of popular thought about single baskets, but I think the shots made from the single NP basket are the best (using the above quantity).
Water tank: Clearly one of the best design features of the SL90 is the water tank. It's really easy to use, easy to see the level and quite convenient to access. If you're able to swing the tank around the side of the SL90, it takes very little vertical clearance to lift and remove the tank. With a 3L capacity, it really helps reduce the amount of refills needed.
Auto-timed features: The keypad that allows you to select up to 12 preset timings is largely useless if you prefer to watch the shot and manually stop it when it begins to go "blond". That's what I do and I think it's essential to getting the best from the SL90. Because of the differences in coffee bean varieties, roast levels, grind etc, you cannot really depend upon a pre-programmed time to be correct for each pull IMO. However, I use the presets for cleaning and running a certain amount of water through the PF. In that regard it's a useful option that the SL70 doesn't have.
Making multiple drinks (entertaining): This is where I feel the SL90 falls short of my needs. I'm often in a situation where I'm needing to prepare 6-10 drinks in a row. The small size of the SL90 boiler injects a delay in making even simple drinks like Americanos. You've got to wait for the boiler to recover each time you need more water or steam and this adds up to feeling like it's taking for ever when you have multiple drinks to prepare. For just one or two people this isn't much of an issue, but begins to be one for 3+ people. For entertaining the SL90 isn't fun to use and this is where larger boliers and HX technology start to pay off.
Long Term outlook: I'm already actively seeking an E61 HX class machine and expect to replace the SL90 within a few months. However, for what this machine was designed to do, it does it very well and I am more impressed with it after several months use.