I was looking for a wide angle for my D70, this came up on clearance, its the "DG" version.
I was looking at various options for wide angle, the Sigma 10-20, sigma 12-24, tokina 12-24, I didn't look at the Nikon options mainly due to cost (I'm not earning money from photog, so I have to justify to my better half ;-0)
This one was near the top of my list because it is cost effective and full frame should I ever get (or Nikon ever make) a full frame camera. Did a lot of reading and kept coming back to the 15-30...
I have only had it for a week so far, so I haven't seen all the pro's and con's. I have shot about 100 frames through it walking around. Seems to focus accurately and quickly, only hunts in low light (nothing unusual there) very sharp around f8, bit softer at max app. Colours come out very nicely, and I'm enjoying the wider angle, my widest lense before was the 20mm F1.8 sigma (also very very sharp lense... maybe I got lucky twice!).
Some CA at extreme contrast changes but nothing bad, only really notice it when "pixel peeping".
Flares sometimes when the sun is in or near the edge of the frame, haven't seen a really bad one yet and it seems to keep its composure when it does flare a little.
The only issue I have really is the filter mount, or rather lack of. The ring for the lense cap has an 82mm thread, but with the standard UV filter I put on it to protect the protruding front element it vignets (sp?!) at 15mm (even with the 1.5 crop factor) and is ok again at 18mm which is a little anoying. I may try to find a low profile filter to see if it fixes the problem.
Its a bigger lense, but not really that heavy (compared to say my 80-200f2.8 AFD), the AF/MF switching is stoooopid, why couldn't it just disengage the camera's AF drive when the ring is pulled back for MF?! Then it would be quite usefull, now all its really good for is to stop the focus ring from turning when its in AF (have the same gripe with the 20 f1.8). AF motor is fairly quiet, unless it has to sweep the full range, but not as noisy as the 20 f1.8 (BZZZZZZZZZZZT beep beep...you may now shoot).
In short, love the wide angle, love the image quality, the lense looks like it means business (if thats important to you!!!). Maybe I got lucky with a good one I have had no probs with both my Sigma products thus far... All in all I could easily see this staying on the camera for a while!!