One gripe about STM(at least the 40 STM) is that the focus ring is decoupled from the actual focusing mechanism, it might be a hassle for some..
Yes i agree, as good as the STM is, the lack of a focus scale and the fact that rotating the focus ring doesn't mechanically focus the camera but instead act on a motor which does the adjustment for you, might make it tough to do manual focus.
As someone who enjoys landscape photography and uses manual focus often, i would still prefer the EFS10-22.
I have the EFS 18-135, and the STM system can get tricky sometimes. Great for autofocus though.