YMMV but I've found the GIMP UI to be pretty much on a par with photoshop after having learnt the UI and learnt/modified the keyboard shortcuts. Some things are in fact better in GIMP, like panning and zooming. I've transitioned to GIMP on my own hardware but still use photoshop at a workplace.

If photoshop was open source then I think there would be a conversation to be had but I wouldn't pay for it now that I'm used to GIMP.