Yeah I've just double-checked. It can.. just. It's the last supported model. However - I can't think of any technical advantage Mountain Lion has over Snow Leopard at the moment. All they've done is add features from iOS so far as I can tell, and not actually updated the system itself.
It wasn't new when I bought it; it was second hand (couldn't afford a new one). I've already replaced the battery twice, since the first one was faulty, and it was half-charged, plus I did a few battery cycles before using it for real. Also I don't think the battery life on the 2008 models are 7 hours... more like 5, or 3 if I run it on High Performance mode.