I'm a bit late to the party on this as the OP has already returned the lens. I did read the thread last night, however as I was on my mobile device I couldn't really comment about the image quality. Now I'm on my desktop I can comment.
For the price of the lens I would say the results are acceptable, and perfectly usable. I've compared the first image to similar that I've taken with my Nikon 10-24, and yes the nikon is sharper, but it's also about twice the price (If WHE is anything to go by). That said I've not seen any crop format UWA that delivers anything like the sharpness you would expect from pro, or even high end consumer, normal focal length lenses. IMO the purpose of UWAs is to capture as much of the scene as possible, so if you find yourself need the ultimate pixel perfect sharpness because you need to crop then the UWA was probably the wrong lens for the task.
I too think there's way too much pixel peeping going on these days, and yes I'm guilty of as well. It's just too easy to pull up an image to 100% and say "that looks crap", when in actual fact it'll probably print at A3 without any visible problem, and still be able to produce an acceptable A2.
For the record I'm not criticising the OP's decision to return the lens. As I've always maintained, if you're not happy with a product for whatever reason then definitely return it. I must say though that when it comes to crop UWAs I consider them fit for purpose, but none really shine.