ya. the distrotion looks bad here.
Hiya, agree with what is being said so far - especially about how one must really know what this lens is for.
This shot that shows bad barrel distortion is just unfair - it's an architectural shot.Most ppl who do this kind of shooting normally shoot with primes. You are never going to get no distortion on an 18mm shot like that with a zoom that starts off at 18mm, or 17mm for that matter! Try the 17-55mm in such situations, you will get distortion as well.
Enjoy the lens for what it's worth, I'm sure you will grow to appreciate how good it is, even if it does not fit into you normal shooting style. If that is so, you may want to consider the 12-24mm for shooting wide and/or the 17-55mm and/or a pro grade long telephoto. All in all, that may cost you 4 to 5 times more than what you paid for the 18-200.