I'm a HS senior too, and I'm planning on getting a 15" MBP to replace my 17" PB during the summer. I've had my PB since I started HS, and I plan to use my future MBP through college.
I went to the Apple Store yesterday, and maybe it's because I'm so used to the 17" screen; I just felt more comfortable with the 15" screen size compared to 13" (I love the glossy screen option!). I'm also partial to the aluminum casing aesthetically, though it does scratch a bit.
I'm just REALLY hoping that Apple will release a new MBP with a new enclosure that looks different from the PB, though unfortunately I don't think that will happen.
(originally, the plan was to give my PB to my parents so we could use iSight/iChat, but now that Apple's stopped selling iSight, I don't know...)
