That's actually a damned good deal. I would definitely buy it were it not for me saving up for a good digital camera. Usually externals are about 50% more per gigabyte than an internal (unless they've changed drastically as of late), so that ain't bad. I have a Maxtor OneTouch 160GB external I paid about $300 for when it first came out. Love it. Best way to back up large quantities of things (my My Documents folder is 41.5 GBs in size [and no, there is no porn in it]). Also good for moving lots of files from one machine to another relatively quickly if they aren't close enough to use a crossover cable.
@Moskie: You can usually take it out, but external HDs are usually used for additional space. Very rarely do you find external HDs with proprietary wiring that require them to be used in their enclosure, but I've seen a couple. They can be very useful for someone with a laptop who needs extra storage space or just to have a backup of all things on your computer to put in a fire-proof safe. I've also seen them used by ameteur film people to store the gigs of digital film recorded before editing it. They aren't great for running an OS or any program on though.
@ Kadath: Who would want a Samsung HD?
But yeah, with rebates you can usually find a decent Seagate, Maxtor, or Western Digital drive of a comparable size for that price.