I just bought it yesterday, but so far i like it.
af speed and picture quality (?) on nikon d700 are good :)
its small and light, built quality is ok but not great.
you could take a look at sigma 24-70 2.8. i used this lense on my pentax and i liked it. it has great build quality but is big and heavy compared to the tamron lense. i think af from tamron is a bit faster.

