Apple's Where To Buy Page
1. If you're a student, buy from the
Apple Store for Education for the student discounts.
2. If you want a custom configuration (bigger hard disk, add Bluetooth, a Super Drive or AirPort to a model that doesn't come with them) then you'll have to order from the online
Apple Store. But buy memory somewhere else; Apple's prices are awful. (The online store does charge sales tax.)
3. Otherwise, buy from the store or website that will offer you the best deal. Amazon.com sells Macs, usually with free shipping, and no sales tax most of the time. [EDIT:
Amazon has a $150 rebate on Apple notebooks today. ] If you don't want to wait for shipping, buy from your local Apple Store. CompUSA sells Macs, too. And sometimes you can get better service from a local Apple Authorized dealer; check the Yellow Pages.
Check the return policy. Especially if you have to ship it back.
Regardless of where you buy, you can get warranty repairs from any Apple Store.