Tokina 12-24mm is great lens, very well build and optically correct.
AT-X 124 PRO DX II has built in motor so it can be used on every Nikon (D40,D60,D5000 and all others).
At the current price level it is probably best buy ultra wide DX lens in my opinion.

What about the Tokina 12-24mm?

I don’t think that the build quality of Sigma lenses is proverbial or idiomatic, it is just not as good or consistent as Nikon or Tokina, the fact actually valued by some people as well as manual focus override that both very much affects the typical use of this or any other lens for me.
It does not have to be a Nikon lens no matter what, but if IQ, usability and everything else is better what exact methodology do you use to say how this relates to the price, for example what measurable parameters would you use to evaluate IQ and price difference between 200-400 and 70-300 Nikon lenses.

The Sigma 10-20 is built like "the proverbial", and for the typical use at these focal lengths the speed of focus and manual override are not factors. Likewise "slower and noisier" for the Tokina doesn't affect typical use for this lens.

So, apart from the "it must be Nikon" school-of-thought, basically it's down to IQ v. price, and there's not enough information available to make a judgement.

Nikon 10-24 is more useful, better built, faster to focus, easer to manually override AF if needed, sharper and therefore better than Sigma 10-20.
Tokina 11-16 is build very well, but it has much smaller range than Nikon or Sigma, and it doesn’t have built in AF motor that makes it slower and noisier to focus.
I actually find all these lenses pretty good and your choice should depend on what you could afford and your personal preferences.
I doubt vast number of reviews could give you a definite answer, more reviews you read usually means you get more confused by author’s personal preferences.

Leon, save your money and go with the Tokina. 10mm is a little wider than 11 so if your obsessed with getting wide, you may want the Nikon. The distortion at 10mm is a bit on the heavy side, so I don't know how useful it will be unless you are willing to correct all your shots. Otherwise, the Tokina gives you a solid and more impoortant fast, lens that performs well.

As far as DX vs. FX... well lets just say that if you want FX, you only really have 1 option. The good news is its the best wide angle option on the planet for the 35mm format.

ugh i hate to spend so much money an a variable aperture DX lens!

Why? Why is it so much better? I'm waiting for someone to do a comprehensive comparison of Sigma 10-20 vs Nikon 10-24 vs Tokina 11-16. One has the best bang for buck, the other has the best range, and the last has fixed, fastest aperture and toughest build.

I wish one of them would just blow the others away and make this decision easy!!

Good choice really if you can afford it, Nikon 10-24mm is better than this Sigma in every angle.

I was considering sigma up till now, mainly because it offered the widest focal length and presented quality. Now im decided on N10-24, since it is finally available. I didn't buy nikon camera to feed it with 3rd party lenses.

I may be a little rood, but Ken Rockwell actually makes very good living from talking nonsense about photography on his Internet site because this attracts people. And by it I mean exactly the kind on nonsense as this statement about DX dream team.
He makes money from the number of hits so of course he is putting his unfinished review right out hoping to earn something.
You should not take his work seriously, it has a little to do with his relevant opinion or expertise in photography but with profitability and that is something I really could not blame him for.
Having tested 10-24mm lens myself I must add that I actually agree with him on most other statements about it.
There is one thing, this 10-24mm is a bit expensive, 12-24mm is still a bit better and not much more, and if you are tight on budget Sigma 10-20mm could be a good choice.

He's odd. I mean, I do read his stuff a lot, but that's because I haven't found anything better to read on Nikons on the internet. :D

I saw his review. It's ok for a review he hasn't finished yet. Hopefully it will be just more review and little more crap like this:

"This 10-24mm is now the foundation of the Nikon DX Dream Team. The Nikon DX Dream Team is now this 10-24mm, the 35mm f/1.8, and the 55-200mm VR. These are all anyone needs in DX, althought many people buy more."

He can't say what anyone needs as we don't all shoot like him.

Just a heads up, I know some of you aren't to fond of him but FWIW here is Ken Rockwell's review of this lens looks like he still working on it but its 99% complete.
http://www.kenrockwell.com/nikon/10-24mm.htm