I was in your shoes a couple of months ago..I have a powermac G5 and a dying macbook, so I decided to get a new pro when they got refreshed. It is an amazing machine, I would be 110% happy with it if...the ipad hadn't been invented. Seriously, get yourself a desktop with a nice screen (24" or +) = imac 27" or macmini..doesn't matter really. I am taking an engineering phd and the mini is good already for your needs..(my old 1st gen macbook still is anyway).
If the ipad isn't enough for when you're around (but believe me, it is), get a white macbook...with those specs still kicks it!
You'll be an happier guy...and your bank account will be too!
I already have an very powerful PC desktop (well, it was when I built it in January 2009) with a 26.5" screen. I don't ever want an iPad, but that's another story altogether.