JD combines the advantages of a sophisticated backup program (versioning, backing up only changed portions of files, multiple back up jobs) and a good Network Drive. I back up all my user files with two different backup jobs, one hourly, one daily. I also use aliases (actually Dragthing items) for fast access to those files. Of course one can just treat the drive as an ordinary network drive--copy files to it and work with files on it. Note that you can create as many drives as you need, and also backup multiple computers to a single drive. For the best features, pay for JungleDisk Plus and get web access away from your machine.
Backup with JD and Amazon S3 is much faster than it is with other programs that I've tried. Even so, an initial backup might take days if you have many GB of data. Start with essential files and add on, rather than trying to backup everything at once.
I think that JD lacks one feature: the possibility of restoring files by DVD or portable hard drive. Carbonite, Mozy, and BackBlaze (I believe) all offer this option. Some companies also offer the possibility that you can ship a portable drive with your initial backup on it.