After two months with this machine, and putting significant amounts of time into learning how to adjust it, I am very pleased. I get very nice shots - rich tasting, full bodied, good crema, not bitter or sour. With all due respect to the PID'd Sylvia I had before this machine, which treated me very well, I nonetheless think this machine produces significantly better espresso.
My routine is to let the machine warm up for at least 30 minutes, then draw off about 8oz of water, and then make the espresso. I now have one of the control buttons configured to dispense the 8 oz of water and stop automatically - a nice feature. I'm still working on getting another button to dispense a 28-30 second shot [more about this below]. But this isn't a major bother and I'm sure I'll figure it out eventually.
The automatic backflush mechanism is very handy. I backflush with just water every week, and with Carfiza every two weeks.
I changed the gasket with the slightly slimmer one that Chris Coffee sells. I also added their cation filter (http://www.chriscoffee.com/products/home/isomacparts/softner), which fits the inflow tube well. I use well water, so I'm using the filter for water hardness and the particulates that are in the water.
A disclaimer - I am not a milk drink person so I can't comment on the steaming mechanism. I really debated getting an HX machine for quite some time because of this, but I'm glad I bought this mchine. Someday I might start making cappas. I'm confident this machine will do a good job wth them.
Following are comments summarizing my experience with temperature tweaking, preinfusion, and then Jim Anslow's comments about descaling.
I was fortunate in getting this machine when I had the week off, because I probably spent the better part of that week learning how to adjust the pressurestat and then adjusting it. There are at least two versions of the pressurestat. As a result, the first information I found on coffeegeek about changing the pressure was wrong for the machine I have. On my machine, you have to rotate the pressurestat control ring counter clockwise to decrease pressure [and thus water temperature]. Apparently another generation of the pstat required exactly the opposite - turning the pstat control clockwise to decrease the pressure. Since I was also advised to adjust the control, then turn the machine off, empty the boiler, turn it back on, and then wait 15 minutes before trying the water temperature, this proved very time consuming. Again, though, I got it to work and am in no way mechanically inclined or gifted.
One of the main problems with this machine is getting preinfusion to work. It appears that there are a number of generations of the controllers out there, in addition to different generations of other system internals.
To try to help, I'm going to give two versions of instructions for preinfusion. Mine is now working, at least partially; the 1st and 3rd buttons from the left have it; the 2nd and 4th don't. I may do more experimenting, but since this is all I need for the moment, I'm not in a rush to do so.
Both sets of instructions below came from Jim Anslow, who sells these machines and is the fellow I bought mine from.
Version 1, which worked for me
"To turn on the pre-infusion for the single and double (the left 1 and 2 buttons (reviewer's note - this turned it on for left 1 and left 3 for me) :
Turn the power off, push and hold the far left first button on the key pad. Turn the power switch back on. The first light and the third light will come on, release the first button, then turn the power switch off.
Now the first two buttons will now have pre-infusion, a short blast of water, then a pause, then the rest of the brew dose will be dispensed.
To turn off pre-infusion <I haven't tried this>, turn off the power, push and hold the second button from the right, then turn on the power. Two lights will come on, now turn the power switch off, then back on, then test the first button. Pre-infusion will now be off in the program."
Version 2 - This contradicts the first version, saying that to turn it on you turn the machine off, hold in the second button, and then turn the machine back on.
There's been controvery on the forums about whether hx machines should/can be descaled. When asked about this, Jim Anslow said there is no reason not to descale this machine with citric acid every 6 months and I plan to do so. As noted above, I also use a small cation filter with it which I got from Chris Coffee.
To sum things up, you should be prepared to put a fair amount of time into getting the machine to do what you want it to do. At the price I paid, I think it was an excellent value for the money. I wouldn't pay the $900+ that they're going for now, but if you can get one in the $550-650 price range, I think they're worth it.