Lastly, the power button rests on the back of the case. Though I personally didn't observe this, a few users online have pointed out on Amazon that this can result in you inadvertently turning it on and off whenever you lay it down against a flat surface. Again, I hadn't run into any problems with this, but it's something to be aware of.
If you plan to use the Anker every day I'd steer clear of it. Its design flaws get annoying over time and it's better to spring for something more expensive like the Mophie Juice Pack Plus, which has a bigger battery and a more sensible design.
But if you're only going to use it periodically for special trips or whatever, then go for it. For $40, it'll do exactly what you need it to -- fully recharge your iPhone on-the-go -- and the price is a drop in the bucket as far as battery cases go.