For a portable computer, AppleCare is very much worthwhile. These machines take a beating yet are light-weighted and very densely packed. They contain things like batteries, backlit keyboards and internal flex-board assemblies that add complication and points of failure. They're subjected to a lot of vibration, handling and temperature extremes that desktop units just don't see.
As others have noted, you can get AppleCare anytime during the first year of ownership, and you can do so at a discount via Amazon or B&H Photo (bhphotovideo.com). When I made my last AppleCare purchase through B&H, it was registered electronically automatically. I had no trouble with subsequent support events at the Genius Bar, and my Retina Macbook Pro's AppleCare also covered my Time Capsule router when it developed an issue.
Highly, highly recommended.
(I do recommend doing your purchase a couple weeks before your 1-year warranty expires just-in-case there's a snag of any sort. But I've never had one.)