It really comes down to what you are going to do with it. Are you mostly an ITB electronic musician or a primarily audio guy recording full drums?
It really comes down to expandability. Bottom line, do you need expandability? You get one firewire bus, depending upon your needs this might not be enough. For instance many like to record to a separate drive.
Do you really need a 2tb hard drive? Do you really need 16 GB? It comes with 4 from Apple (2x2) and two empty slots and it is much cheaper to buy RAM not from Apple
I'm an ITB mostly MIDI/Electronic guy running Logic 9.1 and I love my 27" i7 (or I will in 3 weeks when they come out with the yellow screen fix).