CS2 is only around 3mb bigger once installed, and its not much different. i used to have it but went back to good ol' CS. i voted CS btw.
I use cs right now, but I may switch to cs2 when I build my new comp in about a week. Just waiting on some more parts.
CS2 is extremely laggy once you have lots of brushes and fonts installed. I would not reccomment it at all. CS is great. BTW, someone asked what CS meant. CS = Creative Suite.