I love it. Not really sure if it's worth the $79 as I can wait if I have to. But it's nice not having to spend $25 to get free shipping and it's nice to have guaranteed delivery dates.
Also, they had a promotion so I got a free DVD worth $29, so it ended up costing only $50. It's convenient, but not sure if it's completely worth it.
On the other hand, I find myself ordering a lot more through Amazon because I have it. I bought some books and CDs I could have gotten for a couple bucks less elsewhere, but just because I had free two day shipping, I went through Amazon. I'm not sure how they're doing with that $79 price point, but if they lowered it (or offer me a special renewal rate) I'd surely renew and spend even more money there.