DR. GERNOT STARKE  Awesome tool, hides the complexity of distributed-backups completely, runs very smoothly in the background, the pro-version allows for versioned backups (that is, better than time-machine!)

I wrote an extensive overview of a full-scale backup strategy for small offices - and CrashPlan provides a major pillar of it! See http://it-and-more.blogspot.com/2007/11/sh-happens-therefore-everybody-needs.html

Additionally: Great and helpful support.

I use CrashPlan on 5 machines with Win-XP, Mac-OS and Linux.  
(Version 11.06.2007)