First test shots with Sigma 10-20. Your thoughts?

[Quicklabs]

Really horrible lighting last night--only shot I could get. Wide open at f4and handheld at 1/15. I do see vignetting, but I think that may have something to do with the lighting; it doesn't seem to show up in any of my other quick test shots.
http://img.photobucket.com/albums/v508/lleepoole/Walltest.jpg
Side to side crop.
http://img.photobucket.com/albums/v508/lleepoole/wallcrop.jpg
Here we are at f8 in better light. Took this at work today. I'm shooting on a military installation and praying the Security Forces don't hassle me.
http://img.photobucket.com/albums/v508/lleepoole/MedCen.jpg

So--anything jumping out at you? I really need to get home from work to get the light.

[Code]

Can't really tell without a full size shot...

Vignetting wide open is to be expected.. what I'd look for is sharpness at the corners. Some corner softness is expected wide open, but check that it is reasonable and that one edge/corner isn't worse than the others. By f/8-f/11 you should have good sharpness edge to edge.