It's basically just a drop in configuration to make it look and feel more like the Photoshop interface. Can you accomplish the same with tinkering? Sure. Do I want the spend all day trying to make it look pretty when I need to actually be working in the software? Hell no. Just drop in the plugin and get to work. It has it's place. It would be less necessary if GIMP default layout didn't suck right out of the box.