I just switched from the MSI Pro2a to the IWILL KA266 about a week ago. Running Win2kSP1, board seems extremely stable to me, but Im not overclocking except for my memory. Hardware configuration is as follows:
Iwill KA266
1.2 GIG T-bird rev "b" (9X133)
256 megs Crucial PC1600 DDR
Elsa Geforce 2 GTS
SBLive Value
Intel 10/100 nic
IBM 75GXP 30gig
Plextor 10/12/32
Only problem I have had so far is with Clive Barker's Undying game which is not supported under Win2000 or NT4, it crashes to the desktop pretty often, so no big surprise there. The only other Iwill board I've owned was a PII slot one board (can't remember the exact model), it didn't have many overclocking options, but I could never crash the board no matter what I tried.