Well, we know 2 things about it - it uses the same chipset as the new Abit (that does 350MHz FSB on a 1066 strap) and it has a 1333 strap, so you would expect at least 50% headroom which would say to me that 400FSB might, at last, be possible. If you use the conductive pencil mod on a 266MHz part rather than the 200MHz E4300, the board will boot at 333MHz/1333MHz so we may, at last, have a decent overclocking mATX motherboard - but once again, I'm not holding my breath!
ASRock do seem to be making some good stuff at the moment. Certainly more stuff I'm prepared to buy that many other motherboard manufacturers.