Where is the challenge. It will take years before you can fill up the 30GB SSD with the system (provided the user data is on another disk). Since I am running Win7 on my SSD, I am costantly hovering around 15GB +/- a few.
The challenge is that not everybody is as likely to maintain a clean system as you and I might be. I think that quite a number of people might find it difficult to stay within 30GB. When I got my 80GB Intel, I was really torn on going with another drive to get to 120GB for my C drive. However, by moving my page file, shutting off hibernation, putting my browser cache on my storage drive, setting system restore to 2%...my install and apps plus 2 games (Wolfenstein and Crysis) is averaging right around 23-25GB. So, I'd be a little concerned if I were in a 30GB...but I am pretty comfortable with my 80GB.