I like using my 55U for a change sometimes, but really I find that you need almost "perfect technique" to use this keyboard right if you want to type on it for the entire day. The keys are rather unforgiving: you must hit the keys at a small range of angles for the keys to feel "right". If you hit a key at a "wrong" angle, the keys are just annoying at best and the sharp edges on the PBT caps can actually dig into your finger tips. Another problem is the space bar: it's not the angle, it's the stiffness when you hit it off center. The experience improves a lot if you press the spacebar closer to center. Alas, as the wear on my spacebar shows, I tend to hit the spacebar at almost the 85% point to the right and this is just bad. I had to constantly remind myself to hit the space bar closer to the center when I am on my 55U. On the days when I am lazy and want to anchor my palm on the wrist rest, perfect technique is just not going to happen and so I happily swap out the keyboard and replace it with something else.
Lately I have been breaking into a Code Clear and every once in a while I come back to try the 55U for an hour or two and that's when I start to notice that it really is the thock-thock sound that I like, not so much about the switch. However, I don't hate the keyboard so to speak. Of the three in the office who had tried my 55U, all three agree that it's a very nice keyboard *if* you type with your wrists in the air. The problem, again, is that this does not happen everyday.
(We had a 45 variable before... the problem is the "a" key being way too soft...)