Yes you can buy the Iphone from the apple store or you can at AT&T or Best Buy! I went to the sprint site and it says (look at the sprint link)
" After Nov. 2, 2008, the early termination fee will be prorated for all NEW contracts, starting at $200 and progressively reducing to $50 depending on the number of months remaining in your contract. To find your contract expiration date, log on to My Sprint, and click plan details to the right of your phone."
The iphone is so cool and you'll like AT&T!