As the previous people said, the only differences are slight power bumps with the Penryn chip, multi-touch trackpad, bigger hard drives. I just bought the last generation MBP 2.4 GHz brand new on clearance a month ago with an education discount for $1699. (Originally $2500) I love it! Could've paid $1799 for a current one, but I only had a limited amount of money and so I figured i'd spend the extra $100 bucks to boost my RAM to 4GB.
I'd say you got a great deal if it's in good shape. Way to be!