2 slots are ddr and 2 slots are ddr2 and you can only use one or the other. That still lets you have 2 gigs though.
The 4x PCI-E slot will only really drop your performance by 5% at most. Probably closer to 2 or 3% unless you have a high-end card. And the 8800s won't work at all on it of course.
It's a very good board as a kind of half way house solution to a good upgrade.
Mine is running at 300FSB with RAM at 187 and low timings. RAM is 1GB cheap dell DDR400.
That gives me 2.1Ghz out of my E6300 which does me nicely. Nice stable performance apart from that but there are issues with the Audigy 2. I finally got mine to work. The only thing wrong with my system at the moment is the dodgy RAM. That's more because it's cheap dell crap then anything else. Getting a few crashes every now and then that requires a reset. I don't think that's the boards fault though.