There is a catch to these drives... I have also been looking at these drives even before they were posted here for a raid nice 4+ disc raid setup.
The main problem is the warranty. It's cheap because you only get a 1 year warranty instead of the usual 5 years for the retail non-enclosured Seagate drives. Upon conducting some "it's too good to be true" research, I found that the drives are in a shell that indicates if they were opened thus violating even the minimal warranty. Whether Seagate was smart enough to mark these drives differently to prevent people just claiming they bought the retail drives with the 5 year warranties, I have found no information as of yet.
For people who just want some big storage now or don't care about rolling the dice for using them in raid, then they are probably just fine. For serious raid enthusiasts, I'd say think long and hard before you buy... I am on the fence, but I think I will pass until I have more info. Warranties matter...