You can select whatever you want to sync to each device. I sync an iPad, an iPhone. an iPod Touch, an iPod Classic 120, 2 5th generation iPods and an iPod Mini with one computer and one iTunes.
You need to be selective about what you want iTunes to sync for each device. Most of the time, I elect to sync selected playlists only on the devices with smaller capacity, while on others I sync all music and no videos.
This video tutorial has some good tips about syncing:
http://www.apple.com/itunes/how-to/#video-sync