"I highly doubt I'd sidegrade my 10-22mm for this..."
"I'll be keeping my 10-22mm for a bit longer"
"not nice enough for me to switch from my 10-22"
Typical responses from owners of existing lenses that are 'threatened' by the new lens. Same kind of resposnes from owners of 24-105 when the 24-70 f/4 was introduced, and the 70-200 f/2.8 owners when the Mark II was introduced.
Without any reviews, these folks were able to determine that the new lens is inferior to what they already own. Impartial conclusions, or divertiture aversion?
Or, maybe these folks are right on this one. The 24-70 f/4 and the 70-200 f/2.8 II were more expensive that what was previously offered. The 70-200 II was an upgraded version, whereas the 24-70 trades focal length for some IQ and macro capabilities, but it still costs more. This one is designed to be slower and to cost less than what is in the market (10-22). The MTF charts don't look radically different, so at the end of the day it may come down to IS and price versus aperture, build quality.
You see the same kind of reaction from existing 16-35 f/2.8 II owners when the 16-35 f/4 IS was announced on the same day. Now this one is a cheaper and slower lens. How do you explain that? It's a cheaper lens that has IS and a better MTF chart, despite losing out in other areas. Perhaps that lens was to replace the 17-40, but 16-35 f/2.8 II owners feel the need to defend their choice of lens as well.
As for MTF charts, I can easily put it another way, of the 3 crop sensor Canon UWAs, the 10-22 is the WORST performing, beaten by the 11-22 and 10-18 that are both cheaper and IS equipped.
Actually I don't see the 16-35 f/2.8 vs. f/4 IS discussion nearly as contentious as the 24-70 f/4 IS or the 5DII vs. 6D. I don't think 16-35 II users feel the need to defend the 16-35 II versus the 16-35 f/4. For those of us (me included) that have it, if you need f/2.8, then the 16-35 II is your only choice. But I'm considering swapping the f/2.8 for the 16-35 f/4 IS, just like many in this forum. Would I prefer a 16-35 f/2.8 III that is as good if not better than the 16-35 f/4? Yes, but then it's not out yet (if ever), so that is not a choice for now.
And too bad you can't use the 11-22 except on the M, so that is not germane to the discussion. And no, the MTFs are not that different between the 10-22 and the 10-18. Losing 1 stop on APS-C is a much bigger deal than on FF.
I do think the 10-22 and 17-55 will be replaced and those will be much better than the 10-18, but those aren't out yet, and you're comparing new lenses to those nearly 10 years old.