I have just started my search for a uwa.
Am using a D80.
Naturally....
Tokina 12-24 / f4: Decent quality at good value
Sigma 10-20 / f4-5.6: Really wide angle but slower aperture, at good value too
Tokina 11-16 / f2.8: really fast aperture at good a value
Nikkor 12-24 / f4: ??? at a...