BTW, just for kicks I mounted the DX 12-24 on my D3 to see how it worked in the full-frame/non-crop mode. Big black vignette circle around the perimeter at 12mm, as expected. As you zoom out, however, the vignetting disappears at about 15-16 mm. Given that this lens performs as a defacto 18-36mm on a DX sensor, I've actually gained a bit of wide-angle on an FX camera. Sure, I've lost a bit at the other end, but then I didn't buy the 12-24 to use at the long end. The upshot? In an FX environment the DX 12-24 is everything it (usefully) was in a DX environment, plus a bit more at the wide end where you want it, and without the distortion problems the lens displays at the 12mm setting.
As for the 17-55, an excellent lens I use extensively on the D200 and D2X, the new f2.8 24-70 is a superb replacement for FX use.