Mind sharing your 11-16 story?
Meaning if I even used one? Nope, didn't own it hence I don't have a story share. But if you meant why didn't I choose 11-16 over 10-24?
Reasons for choosing 10-24 mm over 11-16 mm:
1) Wider by a few degrees - 109 versus 107 deg (one degree difference is already a big deal for an UWA)
2) Quality Control - Haven't heard much about Nikon's QC, but Tokina's - a gamble and hassle if you have a lemon (don't take my word for it - just do a search)
3) Longer range - UWA to moderate WA, versatility - allows closing in without the need to crop.
4) Better flare control (you have lesser worries and lesser angle contraints)
5) Distortion control is good from 14 to 24mm - whereas 11-16 has distortions across the range, except the middle I think - better refer to KRW's reviews. But of course, correctable if you have the software support (which I don't).
6) Better resale value (though it wasn't in my criteria since I'm for keeps, but you'll never know eh?)
And sure, I'm aware that it isn't as fast as f/2.8. Since my priority of using it is landscaping, speed isn't a major concern - low light and indoor shots is second priority (I'll just have to boost up my ISO level and accept whatever noise it has to offer). Or fork out for a dedicated prime for low light street usage like 35mm f/1.8?
Hence, Tokina 11-16mm isn't a bad deal (cheaper, built like a tank and much better at low lights). It depends on your priority (landscape versus low-lights) and your budgetary concerns.
Let me sum up Tokina's advantages over nikon's:
1) Fast lens - f/2.8 low light king over the pair. Hence you can use it for landscape as well as indoor / low-lights hand held (provided you want an UW angle for that shot)
2) A lot cheaper!!
3) Built like a tank (better quality body) - provided you don't mind 100g heavier.
4) Sharper at the edges wide open (only useful if you must have it at the larger aperture always)
For me, the advantages stop there... if anyone cares to add to the list, please feel free to add.