Networked, incremental backups are definitely the way to go.
Sending things to another machine is much easier and more
reliable than tape. And it sucks to pull a backup file only to
discover you'd screwed it up before making a backup.
rdiff-backup avoids these problems.
It's also the only such tool I've seen that can handle Mac
OS X resource forks. (With 0.13.2 or better, IIRC.) These are
more important than you'd think - Quicken, for example, stores
important data in them.