I've only used CS5 for a few hours, but I have to say, this beats The Gimp hands down in every way... The content aware fill is by far the coolest thing I've seen in a long time, and the ease of making a lot of my "common" tasks (for example Unsharpen mask on luminosity only) is awesome. Don't get me wrong, The Gimp is great, particularly with the Scheme scriptability, but there's no question Photoshop / CS5 is vastly superior. I'm still running the trial version on my Windows7 VirtualBox installation, and so far, it rocks.

Update: Yes, there is a similar plugin for the Gimp...