The flower photos are fantastic. This lens is the sleeper of the Tamron line.
I also own the 24-70VC for my Canon. I have owned many L lenses and most recently sold my 70-200 2.8 IS after seeing the Tamron 70-300 VC at WPPI.
Yes it is plastic and light. Yes it is "consumer grade," but for $300 after the rebates it is a keeper. The only thing I miss is the 2.8 in my 70-200. Otherwise, this lens delivers in a big way. I have most recently gotten into videography after many years of commercial then wedding photography. I love this lens. It is sharp, quiet to focus. The VC works great. Did I mention it is light. I am getting old and do not want to carry tons of heavy glass. This lens along with my 6D and the 24-70VC is all I need to deliver pro grade images. Let's not forget the 6 year warranty from Tamron.
I also have the 90 macro from Tamron... An all Tamron line up! I never thought I would use only Tamron lenses for paid assignments. If only Tamron made a decent wide zoom. Their 10-24 is soft and not suitable for pro work.
Hope I did not bore you with my Tamron stories. BTW, they had vey cool presenters at their booth at WPPI who use Tamron lenses for fantastic results.