I was going to post a similar thread. The mobo I have coming (delivery pushed back till Monday) is the IWILL KK266-R. I HOPE I don't receive one with the "8.5 CPU Multiplier Lock" problem. If so, its on its way back to IWILL for a no-charge replacement.
I installed the 4.28's on a system with a Via Apollo Pro 133 (non "a"

chipset and they seem to be pretty well suited to the system. It was built for my brother who has "low system" requirements.
The I-WILL support page for the KK266-R, however, recommends using the 4.23's!!!!
Hmmmmm!!!