Similar experience here. I also found that Wal-Mart has a similar selection (lower prices for some items) to Amazon. It shares the same price threshold for free shipping, and also arrives sooner (reliably two to three days from Wal-Mart in my area, versus five to seven from Amazon without Prime).
For me, I go without, and I only buy things with free shipping, so having Prime would not save me money; it would cost me money.
(I also buy less things when I do not have Prime, so that saves me additional money!)