I've also used Mozy since its beta days and I can confirm that it has become very robust about finishing backups if there is a problem on the server end. I've had to contact support a few times when I had a corrupted configuration file, and it's always been prompt. I recommend the live-support, for instant help.
It's true that the backup statistics can be confusing. In my last backup after a reinstall of the configuration (see tip below), the status window said I needed to back up 9 Gig of data. Mozy had lost track of what was backed up. In fact, most of it was already on the server and the total backup took "only" 9 hours.
I've done many restores, and I prefer the web interface. The site packages the restored files in a dmg disk image, and notifies you via email when the restore is ready. I especially appreciate the availability of previous versions. Mozy is very good about downloading package files, which are actually folders.
I also use Jungle Disk for frequent daily backups of my current project files, as I can access them via the Network Drive. However I consider Mozy essential, because because the company will FedEx you DVD's of all your restored data for a price. JD has no such option, and so is unsuitable for restoring more than a few Gigabytes at a time.
Mozy offers a limited choice of backup schedules-- at a designated time each day or when there is reduced load on the computer or you are away for a designated period of time. I would like to see the ability to schedule backups at designated intervals. Still, everything does get backed up in a relatively short period of time after the initial large backups.
The configuration screen could also use some improvement. There are two types of backups--designated backup sets (e.g. Mail, iTunes, iCal, Spreadsheets) and designated files. When you open the configuration, you get the backup set screen. Mozy states that "no" files are designated for backup, and starts to count all the files in each type of set. It's safe to close the configuration or switch to the "files and folders" screen, but you might not think so.
I give Mozy a 4 not a 5, because configuration files have become corrupted more often than I like--leading to the need to uninstall and re-install and to do a new backup. Still I have not lost data.
Tip: When you have the configuration set up and working, save a copy of the state.db and state.dump files. These are in the Mozy folder in the Application Support folder of the root (not user) Library. If you have to re-install Mozy, copy the saved files into the Mozy folder.