If you were to run 2 indentical systems (w/ one Raptor and another system w/ 2 Raptor's in RAID 0) side by side, you would see a noticable difference in the loading of anything. If you're looking for some benchmarks, here's a good one:
http://www.pcstats.com/articleview.cfm?articleid=1746&page=1
Note that read performance is nearly double in some benches w/ Raptors in RAID 0 compared to just 1 Raptor. That doesn't mean they're twice as fast just 1 drive. However, there's a significant noticable difference.
As for that board you're looking at, i'm pretty sure the RAID is through the nVidia chip. I don't see any 3rd party RAID controllers soldered into the board. So... go for it.
Like pickxxx said, not everyone should blow their money on dual raptors. But if you've got the money, it's well spent on dual raptors in RAID 0. Even if you're only playing games and using the internet.
A lot of ppl around here like to say "RAID is only for ppl who do video editing, photoshop, database, blah blah blah." That's bullshit. People who say that don't even have RAID and have probably never even used it or seen it in action. So how the hell would they know?
I have RAID 0 and all I do is game, surf the net, and unRAR crap. So far I'm glad I blew $300 on these raptors. It is the best investment in my entire system.
-mpjesse