Krita actually resembles Photoshop quite a lot, and while the feature list is impressive, I don't think it replaces Photoshop 1:1 or is even meant too for that matter. Krita is more aimed at digital painting, Photoshop isn't a digital painting application, if anything, that's what Illustrator is for.
For a free application you have to give props to Krita, it looks fantastic and plenty of digital artists and illustrators have been raving on about how great it is since it came out. It definitely appeals to me more than Gimp, but I would still probably use Gimp over Krita for general photo touching and editing though. Even the about page on the Krita site itself speaks of illustrators and more drawing purposes. I mean if it works as a Photoshop replacement for some, then that's great. Undoubtedly a cool application.
Photoshop definitely wasn't intended for the wide variety of use-cases it now supports, but it is definitely the front-runner for digital painting, 95% of concept artists/comic colourists or similar artists I know or have seen use Photoshop. Krita looks fantastic, really capable, but I haven't had a chance to try it, mainly because all of my brushes and settings are in Photoshop.
Most designers I know will draw on illustrator and maybe finish up in Photoshop. Since Photoshop is a sort of common baseline in the industry it's used as a general tool to aid in the finishing of artwork even when said artwork is not really in its domain.
Illustrator seems widely used in brand and web design alright, but for example concept artists and comic artists I know never leave Photoshop, start to finish.
Ignore the names "Photoshop" and "Illustrator"; they are historical artifacts. Illustrator is pretty much the last thing you want to use for doing painterly work. If you see digital paintings, there is a very high probability they're done with PS. Pretty much every piece of concept art you see for a video game was done in PS.
(That said, I'll be spending the next few years doing a painterly comic book in Illustrator, but that is honestly more a function of me having used it as my main medium for fourteen years than it is of it being the best tool for the job.)
I'm not a pro or anything, but for general photo touching and editing (at the level of cleaning up my own photos) I'd use Krita over Gimp; it has all the functionality I've ever found myself needing, and in a much nicer interface.
Oddly enough the one place where I switch to Gimp is drawing, as Gimp has slightly better graphics tablet support.
For a free application you have to give props to Krita, it looks fantastic and plenty of digital artists and illustrators have been raving on about how great it is since it came out. It definitely appeals to me more than Gimp, but I would still probably use Gimp over Krita for general photo touching and editing though. Even the about page on the Krita site itself speaks of illustrators and more drawing purposes. I mean if it works as a Photoshop replacement for some, then that's great. Undoubtedly a cool application.