In my opinion, head-and-shoulders above the others if you only make espresso.
Positive Product Points
Great thermal stability from the e-61 group head. Solid construction. Huge drip tray. Easily adjustable brew tempurature.
Negative Product Points
Dispensing hot water is clumsy. Group head gasket difficult to remove.
In deciding what to buy, I considered four basic choices:
Cheap (like the Carrezza) : obviously price is an advantage, but I was pretty sure I'd be disappointed in the espresso (probably due to my lack of skill rather than the machine), and so I'd just end up buying a higher end machine anyway.
The Silvia: Still cheaper than the "prosumer" machines, but produces great shots. Another plus is the wide base of users. I'm just not interested in the MacGyver-like mod's people make to their machines. I know some people are very much into the process of making espresso - I'm really just interested in a great, convenient shot.
HX prosumer machines (like Giotto, Tea, etc) These can be left on full time, which makes thing convenient, can steam/brew without delays, etc. I gather that the HX makes the machine too hot after awhile, but a blank shot or two brings things back down. These are pricey (although now the Oscar seems to be a nice price point), and since I only make espresso (I don't like the milk drinks) so I felt like I'd be paying for something I mostly wouldn't use.
A spring lever (like the Elektra) : Ok, so this isn't about convenience. They look cool and take up less space. There's something really appealing about the simplicity of a spring - cheaper, more even pressure, etc. than any of the pumps (certainly superior to a vibe pump). In the end, the tempurature stability problems, small boilers, etc. made me decide against them. Why is it hard to make a manual machine with reasonable tempurature control?
When I heard about the Zaffiro, it seemed to be the perfect answer for me - the best temp. stability of anything vaguely in the price range, can be left on full time (or better, all day on a timer), etc. Another big plus for me is the easily adjustable brew temp. - I tend to like shot brewed at a higher temp than most machines are set for. It's easy enough to adjust here that I even adjust for different blends.
It produces fantastic espresso, on par with any I've had, and far more consistently than other machines I've used. I would certainly buy it again. Two positive surprises - the pressure gauge has been really helpful in fine tuning my grind+tamp, and the drip tray is huge. I would definitely buy it again. Here are my (minor) complaints:
Too expensive - I don't really care that it looks good, and I feel like I probably paid a lot for all that shiny metal.
Hot water is tricky to dispense - it starts off as very wet steam, and it's difficult to manage. So, for americanos, I find it easier to steam cold water, which is slower (but maybe tastes better).
I recently tried to remove the dispersion screen to clean it (it's been in use for several months now), and removing the gasket is a royal pain.
Chris' coffee is great, as per all the reviews here. I have no valid complaints. Invalidly, after reading all the reviews here, I had expected something super human, with a fantastic package discount on machine + grinder, lots of useful little freebies, etc. Instead, all I got was a good price and great customer service.