30 Gigs - NO. A 30 gig is really only about 25 Gigs of USABLE space. You lose 2 gigs in way manufs count and then another 3 gigs as you MUST leave UNUSED for wear leveling, CG and Trim to work their magic.
60/64 Gigs is Normally considered the Minimum. Personally I recommend 80 as the Min an the recommended as 120/128 gigs. With 60 gigs, you lose about 10 gigs off the top so that's down to 50 gigs usable. Have 3 Systems, OS + programs, NO GAMES - NO User generated data, and all use between 35->40 gigs. AND that is after: disabling hibernation, limiting page file to 1024 mb, and disabling restore points.
ADDED:
On performance vs size. Normally internally drives over 60 gigs use an internal raid0 config. For instant a 60 gig dive is like a single drive, but a 120 gig drive (internally) is two 60 gig drives in a Raid0 config. Raid0 provides a big boost to sequencial performance and a minor boost to Random read/writes.
.. Then there is longevity. EX say you have a 60 gig SSD with 35 gigs on it, now you start writing to the drive, your writes will be spread over 25 gigs (were leveling sill spread the writes around, and even move files that you only read). With a larger drive ther writes are spread out over a larger area thus less writes per cell.