Appologies for digging up an old thread, but I just stumbled across this and found it quite interesting. It seems the majority of the voices in this thread prefer the old school taper axles, and that a few people have had HT2 fail on them.
Personally I cant understand why this is. My first HT2 was on my roadbike, 2008 tiagra so nothing great. 4500 miles on and its perfect. Have completely removed the cranks numerous times and the BB cups a couple of times to clean them. No problems.
Next I got a Cannondale with a 2008 Truvativ GXP system. 2500 miles later, its still perfect. (Yes I know its not stricktly HT2, but its external bearing so the similar arguement applies). Again Ive had the cranks off at least every week to clean, post every ride in the winter.
I recently bought a new condor track bike, it came with a decent quality square taper BB. The level of flex was ridiculous. So guess what, it got changed to Truvativ Omnium with GXP BB. Now it too is perfect, nice and stiff.
The only way I can see them failing is due to poor maintenance, or poor instalation. But with such a simple process of disassembly there is really no excuse for neglect. Im sure one of mine will fail at some point. but when it does I'll happily replace the bearings and carry on where I left off.
Maybe the only way old UN72's are superior is in their fit and forget nature. As far as I can see, HT2 is superior in every other way.