Couple of tips...
I bought a 40GB SSDNow about 18 months ago, best/biggest I could afford without various TRIM and stuttering issues. Promptly installed Windows 7 on it and it really will transform your computer!
Bear in mind, by default, Windows will create a swap file and a hibernate file the same size as the RAM in your PC, in my case, it created 2x 8GB files, that is instantly 16GB of the 37GB available plus Windows itself. Add in Apple and Chrome creating all their data files on the C partition without asking and you will run out of space very, very fast!
I've made my swap file 512MB, switched off hibernate and system restore and used 'mklink' to create junction points to move things like Apples backups to the spinning disks. Happy enough at the moment but currently looking at drives around the 120GB mark. It's also worth noting that many controllers perform much worse with smaller drives so if you are comparing performance figures, it must be on the size of the drive you are considering.