I actually enjoyed my latest COPA travels. The website is horrible, however, I found that I can do my seat adjustments via thier mobile website - not the app (doesn't let u manage your reservation), but simply logging in to their mobile site.
Their new C chairs are far beyond what domestic F can offer on US carriers, and I found the soft product to be not bad at all (good food, nice service). I guess it's a matter of luck, as with any airlines around the world.
R