First, don't be fooled by the screenshot of Mac OS X (taken from Gimpshop.net), you are still in a Linux site. :)
Time and time again, Adobe's Photoshop seems to be one of the holy grail of Linux applications. At least for my students, they often cite the lack of Photoshop in Linux and the unfamiliar interface of Gimp to be the reasons for not using Linux.
Whilst I agree that the GimpShop.interface is a bit intimidating specially for those familiar with Photoshop, it simply takes a while to get used to it. That being said, however, there is a nifty port that modifies the Gimp interface and make it look more like Photoshop. Enter
GimpShop started as a Mac OS X application but being open source, it was easily ported to other platforms such as Windows, Solaris and, of course, Linux. Check it out and believe me, you'll be surprised to find it eerily similar to Photoshop. :)