ABSOLUTELY worth it! I had it for a year for free, and I got it again last fall to save on shipping (paying $39 for a year membership was cheaper than paying to ship the crates or to go get crates at Petsmart).
Free 2-day shipping is fantastic. I can make as many orders as I want and not pay extra for shipping. Often it's more like free overnight shipping, too.
They have a ton of free streaming videos, not as much variety as Netflix but their picture quality is MUCH better.
If you have a Kindle you can rent a ton of books for free with Prime as well.
I also seem to get free mp3 credits all the time, which I definitely use. I use Mechanical Turk and Amazon Payments, too, and the money I get from those I can use right on Amazon automatically, even if it's just a few cents. I use it to sell back some textbooks, too - I should be getting a gift card credited to my account any time now, and it's more than I would have got selling it back to the bookstore.
If I can get a good deal on it, I will be renewing again this fall. Otherwise I'll have to save up and renew in January, but I definitely think even full-price is worth it.
Oh, and I have Amazon to thank for my Doctor Who addiction, as if it hadn't popped up on Amazon to stream for free, I probably never would have watched it lol
