just took a few shots with the Tamron AF 17-50mm F/2.8 XR Di-II LD SP ZL
the NON VC model (which by everything i read is sharper than the VC model.
it was back focusing on me just a tad but it was enough to see it when compared to manual focus via live view

i did some direct sunlight on metal and got just the tiniest hint of green aberrations at f/2.8
you had to zoom way in on the lcd when you viewed the image to see it, and it was on chrome metal too so....

wide open at 17mm shes a nice lens,, man,,, even at 50mm she's nice...
almost bought it but that tiny back focusing was really pissing me off,, especially after all the crap i went thru with my 7D focusing issues. i just wont deal with it, especially on a BNIB lens.

if i buy it i will make them order me a new one though.
but i am stuck between this and the new 70-300 VC lens from Tamron. everything i have read and pictures from POTN show its a friggin killer lens. better than the canon 70-300 USM IS and very close to the 70-200 F/4L but the L wins out in the end of course.