DP Review: Tamron announces 70-210mm F4 Di VC USD for full-frame DSLRs.

The bottom line is, how much 'focus breathing' does it betray? If you don't know what it is, basically when you zoom the thing out to 200mm, you're not really getting 200mm, but lower. More like 150mm. The 70-200 2.8's betray a lot of focus breathing in general ... the f/4's tend not to. So the 'benefit' of having a 2.8 (and the extra cost) often come out in the wash (bokeh is about the same for 150/2.8 and 200/4). And f/4's tend to be sharper all the way down the line to 200 (or 210, in this case). Which is why you'll see budget-conscious people go for 70-200 f/4's.

Waiting for reviews.