I recently migrated from an 80 GB classic. My library is just north of 50 GB so naturally I was looking for a 64 GB model. But I went ahead and bought a 32 and moved over to smart playlists and I've been more than happy.
Let me tell you, these iPod Touch things can prove to be very useful. I'm a pre-med student and I'm majoring in Health Promotion and Biology simultaneously, there are tons of apps that have been useful for my courses, and the Keynote presenter app (for those of us running Macs computer systems and iWork 09) is so cool when you need to give a powerpoint style presentation. I can't say enough about these little things.
Just set up a few 3 or 4 GB smart playlists to cover your musical tastes, set them up to choose high-rated songs more often, or even select by playcount, and they'll refresh themselves each time you sync your iPod. You've got the next best thing to having your full library with you at all times that way, and I've never been caught without a song when I wanted to listen to it this way.
SLC