These drives have actually been on the market for well over a year now, and I was (un)lucky enough to pick one up last year when my local Fry's Electronics got them in stock. While the drives themselves are handy because of the amount of data you can squeeze into them, making my macbook pro a beast of a mobile studio (at the time I was using it for music production), they seem to be prone to issues.
The first drive lasted about a month, before I almost lost several weeks worth of a project I was working on due to the drive crashing. I was able to retrieve my work from the drive by mounting it externally before it became completely unreadable, and I attribute this to the high density drives not being able to handle the average bouncing around of a laptop in a backpack. When I attached the drive to one of my linux workstations, I could hear the disks spinning up but dmesg wouldn't pick up the drive and they just kept spinning endlessly louder and louder.
The second drive lasted about 2 months before a similar problem occurred, though by that time I had migrated most of my work to a different workstation. I replaced the drive with the original 500gb drive my macbook came with, and I haven't had any problems since.
In short, I'm not sure if the early drives off the assembly line were just prone to failure more often or if perhaps I was just extremely unlucky with the ones I procured. Either way, I am rather uncomfortable about putting any important data on one of these drives in the future until they've been on the market for a while and have been thoroughly tested.