I got a new MacBook Pro 2 months ago. I got the i5 2.4Ghz 4gig ram and love it. I would either get the i5 2.4 or the i7.. the middle one is pointless. I decided to get the i5 2.4 and put a SSD in it. It seems to run just as fast as the i7... if not faster.
Get the i5 2.4 and save the $400+... put it towards upgrading to 8gigs of ram or a nice SSD
If you like the iPad then get that. If you want an actual laptop for doing things like documents then get a MBP. I mean if you're not doing anything graphic intensive/processor intensive then I would get an iPad.
But if you believe those catchy commercials they show on TV, iPad can do EVERYTHING!!!!
/sarcasm
Either the iPad or the 13" would be a good choice for you, depends on if you want multi-tasking or not and the ability to add dedicated apps (non app-store apps)
I'd recommend that you get the 15' i7 and stop worrying about a new laptop for the next 6 years. While usb 3.0 would be a great addition, I think the i7 should carry you over for a while.
If you had been following the thread, you would have seen that I already purchased and received the 13" Macbook Pro and really like it. The more I learn about this thing, the more I love it.
One issue I initially had was why I couldn't maximize a window as I could with a PC in Windows Then I realized I had to stretch the window to my desired size, even hide the dock, and now it's right to my liking.