I was not impressed by the Momentums at all, I A/Bed them (with the shareplay cable) for about 30 minutes against M-100s with a variety of different songs. The Momentums were easier to drive but to be honest the mid-range was lacking in detail and depth. The Momentums do win out in comfort, although this was a test pair in an Apple store so they've been worn out for some time; my M-100s are growing more comfortable daily.
As for the cracking issues, I haven't got custom shields and so I haven't had to fiddle around with the screws and I can report NO cracking. I've been VERY rough on my M-100s, dropping them a couple of times onto marble and gravel as well as forgoing the case and stuffing it in my bag and being generally mean to them, there are only a couple of scratches, I'll call them 'flesh wounds' visible.
Edited by dilinator - 11/26/12 at 1:44pm