When I got my AR, I ended up picking up a Tasco from Walmart, and a Barska from Amazon just to have tubes of varying sizes to play with while deciding on what I wanted to eventually end up with from Leupold, as I find they're the best choice for High quality optics.. they're on the lower end of the top tier, and provide an unlimited lifetime warranty on their (non-electronic) gold ring line.
I found the Tasco to be much less... satisfying than the Barska. Neither is really knock-your-socks-off, but the Tasco felt like it was one bump on the road to the range from broken, while the Barska felt like it was solid enough to be a cheap workhorse for times when fun shooting was more important than squeezing every last bit out of your group size.
As an aside, I was just moving all the different tubes I bought for experimentation, and picked up the UTG 1-4x24 CQB scope. It was much better than I remembered since I didn't spend a lot of time experiementing with it. It doesn't work on a standard profile unless you can get it over the sight tower, but with a flipup front sight, or no front sight at all, I wouldn't mind using it.