Thanks Dave. I love the way you have used a wide aperture to isolate the yellow flowers from the smooth dark background.
I have this lens too, and the Sigma 50/2.8 Macro. I use the 50mm to get really close to flowers and beetles, and I use the 200/2.8 (sometimes with a 2xTC) for anything a little more jumpy. I think it's a good combination of 2 very sharp lenses giving me variable working distance. If you are curious, check out:
http://www.pbase.com/stu_warner Cheers for now. Happy shooting Dave.