Hey! I had x55 and now x56. My x55 was faulty ('mouse' was not working right) and they replaced it with an x56 :). My ones are the saytek ones (which got purchased by xxxxxx and then by Logitech).
I have not use them much.
Overall, buttons feels decent, but not tough. The x55 stick, when changing form top to down, left to right, etc, was not smooth (or I had not trained enough with them). The throttler have problems in both x55 and x56. It is hard to move. It is a well known problem of this model: the grease used do not work very well until it is "warn up". While the grease is cold it is so hard it is easy that the throttler get displaced through the table instead. Montoya have not said anything about this so I guess his stick have a better grease or something, or maybe his throttler rubber pads have not enough dust to slide :). I had to fix the joystick with velcro to the table, hahaha.
The software is pretty powerful and you can assign keys, macros, etc to any button, including convert sticks into other type of controls, etc.
Another thing is that I find the stick buttons position a bit wrong. You have to move the hand too much to reach two of them and not in a comfortable way. Maybe my hand is small??? hahahaha. It could had a bunch of buttons together in the same place instead of what they have done with the stick.