huge performance gains dude. i have the x58 chipset with two nehalem cpu's and its night and day. once you go ssd you will never be able to use hard drive again.
went from a single 640gb to a single ssd and boot times are 10x faster, i can use CS5 photoshop for image preview (even with measly 6gb of ram) and its so damn fast what took 10 seconds to load before takes 2 seconds (with no ram caching).
now if you raid two ssd's you get even more performance. no shock issues, less noise, more power consumption (odd, but i see this), and i can put the ssd to sleep instantly without the spin-up time penalty of hard drive.
full a/v scans take 14 minutes instead of 1.5 hours; backups take 30 minutes over network instead of 1.5 hours (full daily compressed images). updates are far faster.
I can schedule an AV scan and Backup at the same time and have the machine done in 30 minutes and back to sleep where as before my policy (daily full av scans and daily full image backups) would run sequentially and take hours. this converts to energy spent.
IMO you are seriously crippling your setup by using hard drives for the core o/s drive. Keep the hard drives for mass storage.
you can get a cheap 64gb (55 usable) sandforce for $98 (amazon s599/microcenter g2) and give it a shot - if you don't like what you see - return it.
But with a fresh windows 7 install (or osx or *nix) you will see mad gains in usability all over the place.
It is by far the best bang for buck mod these days. Well than and the 3x4gb for $129 (fry's) - that would help alot too going to 12gb. but then you have ginourmous hibernation file and iirc windows doesn't compress that file like the mac's.
Just do it!

then let us know what you think