I have 2 buffalo terastation NAS drives, a 1TB and a 2TB running in Raid 5. The 1 TB is about 2 or 3 year old and the 2 TB is 12 months. Running 24/7, no problems thus far. I was a little sceptical when getting the first one as some of the reviews were not so good but I'm happy with them, do what I need plus I can FTP into them when I'm not at home to access my files.
I use FreeNAS on an old spare PC and do the backups to it with time machine through wireless since almost a year. Of course I use the FreeNAS for many other things too.
I am using a Firmtek Seritek 2EN2 with a few of WD 640 hard drives. It has operated without a glitch for over a year. I leave one drive in for backup with Time Machine and the other is used for various storage. You can hot swap drives so getting a couple of extra drives for media, documents, movie storage is inexpensive and easy to handle. http://www.firmtek.com/seritek/seritek-2en2/ http://www.newegg.com/Product/Product.aspx?Item=N82E16822136218
I use a western digital harddrive to CLONE my harddrive - i don't use TM at the moment but probably would in the future when I have the money to buy a 1TB drive and enclosure.
I have a 320GB iomega minimax connected to the iMac and use SuperDuper! for software.
Also have a LaCie Rugged 320GB for the MBP, which I use with Time Machine. It's better for the laptop because it's Firewire bus powered, so much easier to carry around.