Another Amazon Prime subscriber here, nothing but good to say. I buy just about everything there besides groceries. Free 2-day shipping, or really cheap 1-day pays for itself real quick. Always comes when expected, sometimes earlier. They've been good about resolving any issues I've had.
The video on demand service (Instant Video?) is also really nifty. I have one of those Smart TVs, so I can stream TV shows and movies for free off of Prime (and Netflix). That alone makes it worthwhile for me, as I don't pay for cable anymore. Also, free book rentals on my Kindle (and discounts on buying) pays for itself once again.
So yeah... I have nothing but good things to say about Amazon and Amazon Prime. The service is well worth it for me.