Depending on how much ram you have now, you might notice a big speed difference or you might not notice much difference until you start working with bigger files.
The main reason I have the ram disk setup is that its about 50 times faster then a 7200 rpm drive. Since adobe cs3 products only utilize 3 gigs of ram for files, a ram disk can allow photoshop to use even more of the ram. Then again with 6 gigs on a 64 bit os, 1 gig can be used for the OS, 1 gig for photoshop, and 3 gigs for editing files, that only leaves 1 gig free. This winter I plan on upgrading my main design computer to 16 gigs of ram, 13 gigs of which will become a ram disk and will be used as a scratch disk. Since I cant get flexi 8.1 to install under windows 7 x64, I am going to be stuck with xp x86 for some time.