Windows XP 32bit doesn't support dx10 (theres a half-way hack in, but it's not TRUE dx10)
Windows XP 32bit SP3
(No dx10, therefore dx9) It wasn't toooo bad, few crashes here n there
I was using 10.5 drivers and catalyst control center
Windows 7
I started with the 10.5 drivers/ccc for 7, force dx9 through launcher, it was kinda bad
0.3.1 came out and dx9 became crash every 20 minutes, so in desperation I tried dx10. I was only getting 20 odd FPS, but I managed a full week without a crash, playing between 0 and 4 hours a night.
0.3.2 came out, using 10.5 drivers still, and my dx10 fps has skyrocketed back to the old dx9 levels.
To answer one of your final questions, I've been able to play 5-6 hours straight without a crash in dx10, and have gone a week with varying levels of play, without a single crash, the worst crash streak I've had in dx10 was 3 crashes in one night, spaced out a good hour between 2 of them, and 20-30m before then next, this might have been triggered by repeat map reloads to fix cbill bugs in ToS mode. DX10 in win7 32bit has 1.5 thumbs up from me, just because it doesn crash now and then. You don't wanna know where the 2 thumbs are for dx9.