Summary: I bought this lens for a STEAL of a price through Amazon's Warehouse Deals. I've never bought anything used from them before, so I was a bit skeptical and I was worried that the condition of the lens might be bad. Was I wrong! This lens only cost me a fraction of a new lens... and the lens doesn't even look like it was EVER used! Amazon made it clear that the condition of the original Sigma box was awful and ripped open, which isn't a big deal to me.
Summary: I freakin' LOVE it. I have been using it with my D7000 and my D200, with and without remotes, with and without auto focus, and it preforms well! I was pleasantly surprised with the sharpness of the images it produces! It's my new favorite lens! I feels worth every cent! Thank you Sigma, for making such an awesome and affordable lens!
Summary: No, the construction of this little lens is superb. However, you'll be tempted to shoot 'Fish-eye' views all the time! Use in moderation, save those special effects for when it makes sense. I bought this to use on my D300s, and recently upgraded to a D700. You can easily use this on a full frame camera, just be sure you use your viewfinders marks for composition of your image. A fantastic addition for those unique shots. Built like a tank, great optics.
Excerpt: I use this lens mainly for indoor/outdoor sport events such as indoor volleyball, beach volleyball, triathlons, drag racing and cycling. Special photos taken with this lens has been included in international sport federations websites.
Pros: Consistent Output, Fast / accurate auto-focus, Strong Construction
Summary: The Sigma 10mm fish-eye for Nikon mount is sharp, with good colour rendition across the frame. The built-in hood is probably useful, but as one cannot remove it to check it's a bit hard to tell. This lens takes filters from behind, not in front, but contrary to some comments one can indeed use a filter in this way. However, as there is no front thread, one cannot put a protective filter on the lens.
Summary: This really is a great lens - the sharpness and quality of the results is nothing short of outstanding - certainly on my Nikon D5100. There is everything to like and love about this lens - and it's great value for money, too. An outstanding lens from Sigma. I have other Sigma lenses that have disappointed but this is by far the best of all lenses I've owned. You will not be disappointed!