Consider the 13" MacBook Air. You get a higher screen resolution (same as the 15" MBP), faster SSD hard drive, and lighter body. If you can live without a built in DVD drive, I think its a better value.
Don't get me wrong but I would take the extra HD space and potential for upgrading over super portability and speed... But it would be nice to have!
MBP 13 seems like you get more value out of it. That's where I'm at right now, I'm at a crossroads where I'm trapped between the 13 and 15.
The thing that appeals me about the 13 is that it is significantly cheaper than the 15 inch. I could use the extra cash for accessories and AppleCare. Also, it fulfills my needs. I prefer having a DVD drive because it will be my main CPU.
The 15 inch because its bigger and better in screen resolution. And since I currently own a 15" MBP, I've grown used to the benefits of having a larger screen. I don't mind the size, I am sure the newer ones are lighter and more improved than my 5 year old. The new processor and potential to make it into an even better computer sounds appetizing.
I just don't know if spending an extra $500 will be worth it. Currently, I'm leaning more towards getting the 13 because of the value you get out of the price.
And right now, Apple is offering a refurb 13" MBP 2.4GHz for $1049. Compared to a refurb 15" MBP 2.53GHz i5 at $1699.