One important difference between Time Machine and using rsync.net in the way you describe is that Time Machine doesn't require trusting anyone with your data[0].
Of course, it's possible to have encrypted snapshots on rsync.net with duplicity[1], the method I use. That being said, I have no particular reason to distrust rsync.net, and I have liked the service they have provided. If anything, I trust rsync.net more than other backup providers and certainly more than Apple.
[0]: Assuming Apple hasn't set up Time Machine to secretly send files back to Apple. But if you run Mac OS X, you're already trusting them not to do something like that.
Of course, it's possible to have encrypted snapshots on rsync.net with duplicity[1], the method I use. That being said, I have no particular reason to distrust rsync.net, and I have liked the service they have provided. If anything, I trust rsync.net more than other backup providers and certainly more than Apple.
[0]: Assuming Apple hasn't set up Time Machine to secretly send files back to Apple. But if you run Mac OS X, you're already trusting them not to do something like that.
[1]: http://www.rsync.net/resources/howto/duplicity.html