Oof! Yeah, bad performance is not fun. I haven't had performance issues myself but that's definitely gonna be a turn off if you're experiencing that.

Also, if you're working with other people using Photoshop I can see how that might lead to issues. The PSD export from GIMP has been enough to cover my use cases, as the people I work with usually use GIMP as well but I can see how someone very integrated in that ecosystem could miss features.

UI wise, I can also agree that GIMP by default is a bit lacking in current releases, specifically when it comes to system integration, but this is much better in the beta version with an updated UI toolkit.