I've got an SSD that I use as a boot drive (40 gig). I bought it on one of Newegg's previous shell shockers for under 100 dollars.
My recommendation: if you're going to use SSDs, jump in with both feet first. Budget SSDs are ok, mine nets a 7.0 on the Windows Experience Index. It's actually the only technical bottleneck in my system that has an i7, 8 gigs of RAM, GTX 480, etc..
If I were to build my PC all over again I would have invested in a real SSD instead of dilly dallying with a budget SSD boot drive.