fpl1966: unfortunately, as far I understood, it is not internal fucusing (front lens rotate). Make a bit annoyng using filters as C-PL I think. Not a big issue, you can live with it.
The lens hood would appear to mount to the end of the lens in a fashion that requires the filter ring not to rotate (they note it's a "flower" hood, so not universal in how it must be on the lens). The 28-75mm f2.8 was similar. The barrel extends, but does not rotate and I suspect the same will be true of this lens. It may also be that the front does not extend at all, given that they have called it water resistant. That would be an obvious weakness if it does (and easier to seal if it doesn't).
Plus, you can see that the manual focus ring is near the back of the lens, just behind the gold colored band, which leads me to believe it is internally focused. If the front rotates during AF, you usually rotate the front to focus manually.
davidodd: Honest question. Why would you need IS on a fast lens with a max reach of 70mm? The extra weight etc is significant for limited utility? How many would want to shoot <1/70 for portraits etc?
@cordellwillis; Tamron has only had a couple lenses with the newer USD focusing system (such as the 70-300 f4-5.6 USD VC). My experience with those lenses is that they are nearly as good as the Canon/Nikon lenses. The difference is negligible enough that it is difficult to tell the difference.
The Tamron VC system is really fantastic. If the optics are as good as the 28-75mm f2.8 (I think they will actually be better), then this should be a great lens. Hopefully it isn't too expensive, but how much different is it to make than the 70-300 VC USD? That one runs a very reasonable $450 or so.