I imagine a few people have wondered when I would weigh in, since many of you have read my review of the lens. First, I did return my first copy of the lens. The IQ was great, but I didn't feel the VC was working within spec. The online retailer I purchased from had no problem with this and had me my new copy within a week. My second copy has been superb. I was worried after that first copy, but am I ever glad that I stayed with it and got that second lens. It is my most used lens, and is an incredibly useful tool that keeps impressing me with great results.
It's interesting to me that everyone here has fixated on Bryan's QC issues (thanks to whomever brought up Roger's update that the newer copies of the lens have been very reliable and that the lens has done well) and few people seem to have noted that the Tamron essentially keeps up with the image quality of the 24-70II - a lens considered to be the finest zoom lens to date. Ummm, that ain't so shabby for a lens that costs half as much and adds a killer feature in the VC. I do find the AF slower than L series USM, and I would agree that it wouldn't be a great sports choice because of that. I have taken thousands of pictures with the lens, though, including a lot of time sensitive event work, and I haven't noticed the inconsistent focus that Bryan reported. I have used the lens on a 60D, 5DMKII, and two 6D bodies. I just shot a golf tournament and business mixer a week ago, and was consistently impressed when I zoomed in 100% in LR and saw all of the shots so beautifully sharp. In fact, I came home from the same event and decided to run AFMA on my 85mm f/1.8 again because I was disappointed on the focus in some of its shots.
In all fairness, though, I haven't shot a lot in AF Servo mode. I primarily shoot One Shot mode for most of my work. Because of the slightly slower acquisition time of the AF, I wouldn't be surprised if it didn't excel in AF Servo mode. You have to consider the style of shooting that you will primarily do.
As far as optical quality, however, Roger's conclusions are that their copies of the Tamron are far more consistent than the MKI of the Canon 24-70.