Lets get this one started....
Looking at MTF charts alone, how much better is the 10-22 vs 10-18? If we take the charts at face value, will the 10-22 be sharper or softer? Additionally, even if the 10-18 is a little softer, with it being half the price, would it be a much better value?
The new 10-18 is 2/3 stops slower but it has huge benefits like smaller, lighter, smaller filter, 3-stop IS and cheaper so no brainer (it's a steal). If you don't have UWA go for this. I had the 10-22mm and I was happy and if you have it, there is no sence to go for the new 10-18mm.
Most of those 'huge benefits' are subjective. Even the IS is arguable. I'll concede that I'd rather have it than not, but if it's a tradeoff between that and a wider aperture not everyone is going to choose IS, especially at UWA. Add in the better build quality, distance indicator, full time manual focus, 22mm, and USM and now it's not a 'no brainer' at all. Even the smaller filter size is debateable. All my filters are 77mm, so the 10-22 wins on that account too... for me. And for the final nail in the coffin, I can currently get a 10-22 refurbished from Canon for under $400, less than a $100 difference, if I could even buy the 10-18. I'm not saying the 10-18 won't sell like hotcakes, just that the 10-22 still has its niche.
I am sorry, but I have to disagree.
I owned and loved the 10-22, it is a great lens!
However, there really is very few reasons to buy it any more; good reasons, that is.Build quality:
who cares about pennies. Both have a cheap build quality, just cheap and cheaper
. The 10-22 isn't weather sealed either, and they are both quite plasticky, and similarly likely to break in a fall. A lot has been made about metal mounts, but I am yet to see significant number of people complaining about plastic mounts breaking.
Distance indicator and FTM: How much does one really use those in a WA lens with AF? I use it quite a bit with my Rokinon, however, but never did with my 10-22 (it has markings at 1 ft, 3 ft and infinity, by the way). Only time you might need it is when focusing at infinity (night sky, etc).
USM: Not a big difference between USM and STM in a wide angle lens with such short throw.
Not worth paying more money and losing IS, IMO. No question about it.