Nice shots! Glad you're enjoying your lens. I am enjoying mine more and more now.
I bought the Tokina 16-28mm about a month ago and I love it!
I'm no expert on UWA photography, but I'm having fun trying to get the hang of it.
My first impressions have been that it's very sharp, good color, low distortion, and affordable. A fantastic lens!
There were instances where I had some flare when the light source was directly in the picture, but it didn't strike me as a major issue or big detractor from the overall quality of this lens.
Here are a couple I took recently.