I currently have the 10-22mm on a 550D, but will be upgrading to a 5dmk3 at some point this year.
My question is that I do alot of landscape shots while hiking (though without a tripod). I know that I can't use the 10-22 on the 5d, but was wondering if the 8-15 fisheye might be a good FF replacement for the 10-22mm. Looking over my stats in LR for the 10-22 lens, i find that over half the pictures are at 10mm and alot of the times i wish it was a little more wide. I personally like the distortion on the 10-22mm but if it was a little stronger, I'm sure I would like it. Hence why I started looking at the fisheye. I figured anytime the distortion is not what I wanted, I could just apply the lens profile in LR, though I realize it will result in some cropping of the picture.
I'm just starting out in photography, but it seems that the 16-35L is an ok lens, but not an amazing lens like the fisheye or the 10-22. Long term, I would probably get the 14-30L lens (if Canon ever decides to make one), but think in the short term i could get away with just the fisheye. Oh, one last thing, the fisheye is $600 USD cheaper than the 16-35L in Japan, which is also a factor.
So my question is, does this logic seem sound, or is the 8-15 a really niche lens that won't really fill the gap of the 10-22 for purposes of hiking and landscape shots.