I got mine yesterday and took a few test shots of a classic car out in the parking lot of my office and I've got to say, they looked pretty nice to me! I'll be testing it out much more this weekend but just from my test shots I'd say this is A. going to be a fun lens B. be a lens that has a real learning curve, I guess you can't just shoot
anything with it and C.
the pictures looked nice and sharp at f/3.? or whatever I was shooting at, although I haven't done 100$ crop or anything to really check it out.
I really like to buy Nikon lenses, but that being said, I think my Sigma 30 is my favorite lens yet and it's a third-party---so I definitely wouldn't write them off, especially for more of a specialty lens that you won't be shooting with every day.
FWIW, I am borrowing a fellow Photo DISers 10.5 fisheye right now and it's really fun also. I'll try to post some shots from each in the upcoming week or so if I shoot anything of interest. I have been looking on Craig's List in the NJ/Philly area and found a Nikon 10.5 fisheye for $450!! That's a steal (said the lens was in good condition, but I didn't check it out since I don't have $450 right now to spend).
I'll try to give you a more comprehensive review of the UWA after I do more than just parking lot and living room shots with it.
and wind up saying..nah, ya don't need it, your 18-135 is good enough, why spend the $$, la, la, la.. 
Tomorrow is one year since the start of our last trip.. we know our future trips with our boys will be more awesome than we can even imagine, but man are we having major withdrawals for now!
