Gee. A question such that "I" can actually add some relevant information. How nice....for me. Anyway, I actually own a Tokina 11-16 that I use with my Nikon D90, thank you very much JonnyApple. (He pursuaded me to get the D90.)
It really, really is sharp, focuses well and I "like" it very much and won't sell it. But for me, it does have some drawbacks that you need to consider when deciding whether to buy or not. First, the focus range (11-16). Man, at 11mm, that is Wiiiiidddeeeee. The problem is that at 16, that's really wide also. from really, really wide, to really wide. See the problem? The range isn't broad enough, at least for me.
And then, to add to that the problem that comes with using filters. Yes, I have moved into using filters to help with those problems of extreme range of exposure requirements within one shot. After attending a great short workshop on filters, put on by a young SoCal photog, named Nick Carver, I got the Cokin P series filter Holders (the regular one AND the slim one for wide angle lenses) plus several filters. Listen, those filters are expensive, so I bought mostly Hi-Tech brand. Cokin filters themselves have known coloration problems and are not recommended although they are some of the cheapest. For the P series, it uses these rectangular shaped filters (why they call them square filters is a bit weird).
Well, coming back to the Tokina 11-16, even with the slim/wide angle filter holder, you get serious vignetting on the corners when shooting at 11mm and up towards 16mm. Not good. I really learned this recently at a photo workshop I attended at the Grand Teton National park when I was trying to use the Tokina. I finally took the filter holder off and just held the filter up against the lens with my hand/fingers. Mostly, I got some really great shots of my index finger in one corner. It's hard holding the bare filter directly next to the lens and NOT cover a small portion of the lens. That sucker is wide. I made do, as best I could, but that issue is a clear difficulty when using the Tokina lens with filters. Now you CAN avoid problem by paying really big bucks for LEE filters and holders, but I'm not made of that kind of money.
I also have learned, that for me, the Tokina isn't really that good in landscape shooting situations. It is MUCH more fun and useful in architectural situations or even those landscape shooting situations that use a vertical frame hold and intend to capture some really close detail along with the more distant background. Just dont' have too much distance to your background or the perspective just goes completely out of wack.
So, will I keep this lens, you bet. Would I buy it over again? Probably not, because of the limited focal range. I would rather have Nikon 12-24mm. But that's about three times the $$ of the Tokina.