I don't own a 3 so I'm not up on the rules on purchasing regular apple care, if you can for the 3 and if the rules that applied to my 2 apply to the 3. Namely that I could purchase Apple Care anytime within a year of the purchase of my iPad.
You may want to read and see what you're eligible for. As to whether or not...it's a personal decision. I originally didn't. I bought mine at Best Buy and, of course, had them pushing their black tie service at me and I turned down all their 'extras'. However after a month I had issues with the port on the bottom of my iPad. My port went bad and I was unable to charge and sync it. I took it back to Best Buy and they exchanged it for a new one. I then chose to lay out the money for the extra year due to my experience with one faulty device.
But I know others that never purchased the warranty and have never needed it. So it is very much a matter of personal preference.
How to get AppleCare+
You have 30 days from your iPad purchase to buy AppleCare+.
There are two ways to buy from Apple:
From the Apple Online Store: When you order the new iPad or iPad 2, you'll have the option to add AppleCare+ to your cart before you check out.
At an Apple Retail Store (if AppleCare+ is purchased separately from iPad, a Genius Bar appointment, inspection of the iPad, and proof of purchase are required).
The above are their words. Verbatim. It leaves one confused. Though my understanding was also like yours, that one could buy apple care within one year.
Your opinion does help in confirming my thought that one should have Apple care. Guess will wait & read more.
You could buy the original AppleCare plan, the one which did not include accidental-damage coverage, any time during the original warranty period. Apple no longer sells that plan, though, only the AppleCare+ plan which includes damage coverage. You must indeed buy AppleCare+ at the time you purchase the iPad or within 30 days of purchase.