The GIMP is almost on par with photoshop (considered the best image editing software, so I assume it is superior to ArcSoft in term of features) in term of feature, but the GUI is lacking. It is much harder to use and the dialogs are not that great. GIMP 2.8 will solve many of these problem, but it is in alpha right now (2.7.*). You have two choices, learn 2.6 with some tutorials to find where the buttons are or install 2.7 ans turn on the Single Window mode in the Window menu. Then it will be more tolerable with dockable palettes and some gui improvments. The only "big" feature GIMP is missing is advanced color modes.
You can also try Krita, it is much simpler, but more oriented for drawing and content creation than content correction like PhotoShop. It worth trying anyway.
sudo apt-get install krita