I just got my used copy yesterday, but I've already played with this lens enough that I feel comfortable commenting on it.
First, it's very small and light and that's exactly what I wanted for when my Nikon 24-70 gets too heavy to lug around. On my D600, it actually focuses almost as fast as the 24-70, but it's a bit loud, especially when it clanks against infinity and minimum focus. Aside from the 2.8 pro zooms, I don't think any of the newer AF-S lenses are quite as fast, but the importance of focus speed in practice is hard to quantify.
Sharpness is decent wide open, but contrast suffers a bit (more noticeable in some situations/lighting than others). For some shots, it may even be a benefit. f/2.2 already shows a slight improvement over wide open, and f/2.5 shows a significant jump in sharpness and contrast. By f/2.8, you're clear of anything objectionable, but f/2.5 gets you 99% of the way there.
The color and contrast is more subtle than many newer lenses and is a welcome change (not better or worse, just different).
Overall, I can't recommend this lens enough, especially for the money.