I am a Mac user since 24 years, nowadays using Crashplan+ on a Macbook with OS X 10.5 to backup to a 100 GB account at their data center "Crashplan central" and to a Window Vista PC downstairs:
Works very well with minimal impact on computer performance/usage. It's a real set and forget business and test restores have worked out elegantly and flawlessly. The main thing on my wishlist would be to have a possibility for different backup sets to different locations, e.g. to backup everything to local computers and a reduced set for the cloud.
-Nevertheless, the developers are to be congratulated for top-notch and mature software!!