They, or at least the one i bought comes with in-built backup software which allows you to backup either the whole drive or specific folders with or without sub folders. It can then monitor these and update at regular intervals which you select. Moreover, you can have it "sync" certain folders. What it does is that it makes a copy of the folder, and if you plug it into another comp which you have installed and activated the same service it will copy the files onto the same place, unless the other comp has a newer version in which case it will update the version it has. This allows you to easily switch between for instance the job computer and home computer and have the most recent documents available. Also, encryption. Might have forgotten something.
A drawback is that you can open the case and connect it to a SATA port as a slave (the sata is faster than usb i have heard, might be wrong) so if you, like me, intends to move images, documents and games to the external in order to speed up startup (clearing the HDD from files reduces reading time) it might be better with one that can be opened. Also, if you dont understand half of the above, its tha thaing fer u!
Edit: Just read thoroughly through your post. If you are planning to connect to a sata, better of with one that you can do this on easily, otherwise go. I have no clue when it comes to reliability, i can only speak from maybe 3 months of experience.
Edited by Surma, 20 February 2010 - 05:31 PM.