I like mozy. The price is great- $5 a month for unlimited space. You can't beat that. But I have problems with it:
1) If you reinstall windows, there does not seem to be any way to install mozy to use an existing account. The best I can find is to go into the mozy account settings, and delete the old account, then recreate a new one. But then you need to re-upload everything. If your backup set is 40GB, as mine is, you'll be uploading for a week. Not a dealbreaker, but a problem.
2) The disk usage. My laptop has a 5400 rpm drive, and a lot of disk IO brings it to a crawl. At some point I'll get a second hard drive, which might help a little.
a) Idle disk usage- when nothing's going on, the mozy client is doing reads of Mozy/Data/manifest.dat and Mozy/Data/state.dat. Why not use ReadDirectoryChangesW?
b) The SQLite data store. I presume that the mozybackup service is using the FindFirstChangeNotification API to update a database. (I assume the database is SQLite because the file changes are to a file with -journal suffix.) Reading the change journal seems to be a time consuming enough task, but adding the database journalling seems to worsen the problem. It takes a really long time to get through all the changes (minutes), especially after rebooting. Perhaps if the transactions were lengthened to include more changes the process would be shorter.
Basically, it's a good idea, but needs optimizing.