Well, many things really. I find RAW on Linux not great in all honesty for starters. The GIMP UI is absolutely horrid. Non destructive layers is a big miss, as is 16 bit support for me, since I work with 16 bit tiff files. The GIMP is VERY slow, much slower than Photoshop or Elements. The GIMP help is a horrid joke, I've never seen the help section actually work for me yet in about ten Debian version releases over the years...maybe it's me, but the UI is just well, horrid. And I used the GIMP for a few years before switching back to Windows back in February 2006 (and didn't start using Photoshop until May 2006 I might add). I found Photoshop's UI etc just that much more better. Then there's cmyk support in the GIMP (lacking)...working colour space has only just been included in the main 2.4 tree...then there's the lack of quality plugins, and 3rd party commercial plugins. Documentation on the GIMP is lacking - try getting an actual book on it so you can learn about it more...
Add to that, I'm not a fan of Gnome. Gnome has one of the most horrid UIs of any operating system desktop environment that I've ever used. I would rather work with CDE than Gnome, and that's saying something!
Dave

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