So much to say...
First, you'd probably be just as happy with a 15" as a 17", which, even if you get the top-of-the-line 15", shaves $200 off your edu price.
Let's say you get the top 15", add some options (128MB VRAM, 1 RAM stick instead of two, faster hard drive), and end up around $2500. Or you go with a lower 15" model and spend ~$2K.
Here's what your money gets you - what that extra $1K (it's actually not that much of a premium) buys:
(1) OS X. This is hard to overvalue. OS X is something which is actually cool to use, as opposed to simply being what you need to boot to get to your apps (i.e., Windows). I work on Windows machines in my "real" job and Macs at home. I am never happy to sit in front of the Windows machines - I like a lot of the apps, but Windows is just there. OS X is a fun ride by itself, and there's so much to learn about it to make it more fun, yet it is immediately accessible for beginners.
(2) iLife apps - like Garageband (right up your alley), iDVD, etc. These are pure gold and are included. In fact, here's all that's included:
Mail, iChat, Safari, Sherlock, Address Book, QuickTime, iLife (includes iTunes, iPhoto, iMovie, Garageband and iDVD[4]), iSync, iCal, DVD Player, Classic environment, Acrobat Reader, Art Directors Toolkit, EarthLink TotalAccess (includes 30 days of free dial-up service with Earthlink activation), FileMaker Pro Trial, GraphicConverter, OmniGraffle, OmniOutliner, QuickBooks for Mac New User Edition, Zinio Reader, Developer Tools and Apple Hardware Test
It's a hell of a bundle.
(3) Mac community. Sounds dumb, but the Mac community is generally more supportive than the Windows one.
(4) Ease of use. Not just OS X, but the apps as well. It's just easier to use, period. Except for window resizing - Windows is better at that!
(5) Beauty. I mean, come on, isn't the backlit keyboard worth something by itself?
(6) Built-in wireless and Bluetooth. 54Mbps 802.11
g wireless. Not typical Centrino 11Mbps 802.11
b wireless.
(6) Fun and joy. You'll love a PowerBook. You'll use it incessantly. You'll see it as a tool and not an impediment. It's a wonderful thing.
As I said, I use Macs and PCs. There are things I like about Windows, and about PC laptops. But, generally, the PB is the gold standard.
As far as financing - true, you only pay interest for two years. But... two years down the road, you've paid a lot of interest but haven't
touched the principal. Not a good idea.