Speaking of third-party lenses, the upcoming Tamron 24-70/2.8 Di VC USD is looking very promising. I've always liked Tamron lenses; they're optically excellent and affordable, just a bit under-built. The non-VC 17-50 has served me very well for several years on my 40D, but now that I plan on moving to the 5D3, this yet-to-be-released lens is going to be my frontrunner for an affordable alternative to the prohibitively expensive 24-70L II.
The Tammy promises better build quality and weather resistance this time around, and has that (for better or for worse) three-axis vibration compensation mechanism. I've never needed IS for anything; with the 5D3, I can even shoot at ISO 25600 no problem! I'm only worried whether or not that extra lens element will compromise IQ...
EDIT: I guess I can use the VC for HD video use... handheld shots at 70mm will definitely benefit from image stabilization.
Edited by tomscy2000 - 3/13/12 at 3:05am