I needed a walkaround zoom for my D700, but I simply refused to pay $1000+ for the 24-120 f/4 simply to take vacation shots. I've also owned a couple different copies of the 28-105, which was a good lens as well. But after reading the reviews of this lens, and subsequently finding one, I took a chance.
I'm glad I did, and I've been nothing but impressed with the performance of this lens. It's sharp across the frame, with the exception of the corners. The colors are vibrant and nicely saturated. The distortion isn't as bad as I expected (but not as good as the Nikon 28-105). It's also an older lens that doesn't have VR, or VC, or OS, or whatever Tamron calls their vibration control mechanism. However, I've found that I can shoot at 135mm wide open and still get great shots. I believe the nice heft of the lens strikes a wonderful balance on the D700, and I'm able to hold the camera steady.
It just feels good in my hands. I've tried several lenses that fell in the same general focal range:
*24-120VR (the older version)
None of these lenses combine the sharpness, focal range, build quality, and balance that the Tamron provides. And while I haven't directly compared it to the 24-120/4, I'm satisfied to the point that the Nikon lens simply doesn't interest me. And I've still got a few bucks left in my pocket.