The Zip-Top Shop Bag is utilitarian genius. Like you, I've tried a dozen shop totes that either cost me a couple bucks or were handed out free at some event/magazine subscription, and while I advocate using a "bring your own bag" for shopping of any kind, the bag itself has to be good to be usable. And most tote bags are complete garbage. The Zip-Top Shop Bag is not -- In fact, it is the best tote bag ever made.
The biggest issue most generic tote bags face is the handle. This critical feature of the bag is often the most overlooked design. Oftentimes you're loading things into this bag, and then commuting with it a short distance back to your car, or a longer distance on a bus or bike, and it's imperative that the handle should be comfortable at all times. It shouldn't dig into your palms, and it shouldn't feel flimsy. It should work like a dream. And the Tom Bihn Zip-Top Shop Bag works like a dream.
I can't advocate enough for using this bag. Buy one. Buy two. Buy three! They will last. And those handles will become your favorite thing about them.