Ehhh, that isn't bad, but there are better bikes out there for under a grand. The components on that bike are not that great, and if you decide that you like to ride, you will see their short comings for sure.
First thing I would do is if you are serious about this, go to your local bike shop, and get properly fitted. It doesn't matter how sweet the bike is, if it doesn't fit, you won't like it. Another thing about the local shop is maintenance/tune ups. A lot of shops offer at least one free tune up, maybe more, sometimes for the life of the bike if you buy from them. They will work on that Diamondback, but they will charge you. If you build up a rep with a shop, you are often likely to get discounts on stuff, or they will work with you on getting a cheaper package deal, like some tools, helmet, gloves, etc at the time you buy.
The other thing is buying that Diamondback before you test ride it. Unless a local shop carries those, you are buying without riding. What if you get the wrong size or you don't like the ride? I remember test riding a Gary Fisher before he sold out to Trek, and I hated the ride of it. Ended up on a Specialized and I liked it much better. The Gary Fisher was nice, but the bike felt weird, the geometry was a bit off for my body type, etc. 7 bills is a lot to drop to not be sure.