Another way to look at it, is price compared to total price of your Mac. I bought a MBP with a few upgrades (I did not upgrade the RAM, I know better 😉 ). The price of MBP is already hefty, that a few more bucks (I had it reduced through Student Discount) it really wasn't that much. If I were paying $300+ on something that was $1k or so...well, thats almost a third of the cost of the Mac.
Also, I bought an ACD at the same time which b/c of that was also covered in a single Apple Care, which is basically cutting the price by half (figuratively, its now covering two items).
All in all, I think if you're investing in a Mac, which we all know is a little more expensive than alot of what you can find out there (no matter whether its because of OSX or not) its a good peace of mind [as stated earlier].
Note: Your Mac should last you longer than 2 years, I think you'll be pleasantly surprised!