I love that water drop hanging on the underside of the main tulip in the first picture.
Yeah, I'd agree with Peter Zack - that is one crappy lens. You need to get serious and divide the range of 100 to 400mm into several different lenses. That's the only way a true LBA-afflicted photog would see the problem...
But seriously, Sigma certainly do some very nice lenses, and their bokeh in particular is very good for most of them.
Check the bokeh on some of the shots taken with my new Sigma 180mm Macro, on:
https://www.pentaxforums.com/forums/post-your-photos/26579-first-efforts-post...0mm-macro.html
Particularly the pics of the bottle brush and the frangipanni down near the bottom.
I only just got the lens a few days ago, and I'm very impressed with it. The bokeh on your 135-400 is really nice too, particularly that first shot. Beautiful. Sigma lenses are really setting their reputation up high, and your shots are more evidence of their quality. Very nicely done Stu