As an owner of the EOS-M, and someone who likes to travel light and take landscape/architecture shots, I'm happy this lens is being made. The cost though, seems a high 399 EU (524.68 USD, or probably a US MAP of $499.99) is high. I was hoping this would be more in the $199-$299 range.
As for the higher f-stops. Most landscape shots are done on a tripod, so it doesn't bother me. I always try to bracket my landscape shots, so I'd always use it that way. f4-5.6 is sufficient for lens of this caliber, so long as the image quality is on par or better than the EF-S 10-22mm.