A friend of mine got a 2012 demo Mamba last year for 700. So, yes, I believe that 600 is a great deal. I would suggest doing a few test rides to see if the bike feels right for you, though.

Edit: forgot to mention; my friend is a beginner who only gets out a couple times a month and he absolutely loves the Mamba. Its got solid components, a fork that does what needs doing, and, most importantly, the bike just looks cool.