LightZone
If you long for simplicity in photo editing in an un-bloated piece of software, give LightZone 3.0.6 a try. Its unique visual approach to editing, time-saving Styles, and well-designed help system will aid the learning process. At the speed at which major enhancements are being released, I can’t wait to see version 4.
At the time of that writing, LightZone was a $200+ citizen of the photo editing elites, it has recently became a freeware.
Darktable
That brings us to Darktable, a “virtual lighttable and darkroom for photographers” whose user interface reminds me of Adobe Photoshop Lightroom.
Mark Myerson wrote a pretty comprehensive review of the app which I pretty much agree about.
I have yet to try LightZone, since it’s still on beta for the Mac, but Darktable is available for the big three OSes.