The MBP 13" has a FW800 port. Your old Macbook has half the battery life. It has very very poor GPU performance (using an Intel GPU) compared to even the older 9400m, the 320m blows it out of the water. Aluminium body vs your polycarbonate, LED backlit screen vs your CCFL. Mini Display port capable of much higher resolution output than your mini DVI. Backlit keyboard.
And it still has the line-in port, combined with the out port. Since it has a microphone built in, seems like that doesn't really matter (and USB headsets today are prevalent, compared to 3 years ago when you had dual plug headsets).
CPU GHZ is the last spec you should look at, compared to a 3 year old Macbook, the MBP 13" is a nice upgrade.
For you, it is a very good upgrade. But, if your Macbook does everything you want, don't upgrade. Upgrading for the sake of upgrading is just a waste of money. Some people just get an "itch" to upgrade and do, and in the end, all they've done is create some debt for themselves.