I have the Turbo now. Great and
supremely stable board. I would not hesitate to recommend it without reservation. Still, it has two relatively minor quirks which i think are worth mentioning.
First, the current available BIOS'es out there for the Turbo are not yet the best they can be, and that's been causing some minor headaches for those who like to do 'extreme overclocking.' That's a very fixable problem, and i think it shortly will be. Don't know when, but i have no reason to doubt that MSI will continue to refine the bios until it's virtually perfect.
Secondly, and this is perhaps not a big deal, but there are some very slight cooling issues with this board. Only 2 on-board fan connectors, and the in-socket thermistor for the Turbo boards seem to 'read hot,' that is, shows readings higher than i think are actual (mine seems to, and i've run across some other folks who report the same). It's nothing to get concerned about, just an FYI, and that's one of the inherent problems with all socket-a boards - imprecise cpu temp monitoring via the in-socket thermistor. Go to the cases&cooling forum and you can read all about it.
I've used Abit boards before, and haven't had any problems with them. Abit pushes the envelope with their boards a bit more, both in overclocking potential, and in quality control it seems (one of the higher RMA rates in the biz).
All in all, i'd say that the Abit, while being a bit more finicky and perhaps 'higher maintainence' than the MSI, has a slight performance edge. The MSI board is solid as a rock, you won't be able to make the board unstable even if you tried, but you might not be able to push it quite as far as the Abit. But they're both good boards, and i don't think you'd be particularly disappointed with either.
