This image of a seagull was processed out of RAW using UFRaw and Gimp, running under Ubuntu Hardy Heron (Linux).
I've been using Linux OS and free Open Source software to process my pictures on and off for a week now. There's a lot to learn and I've only scratched the surface.
My early impressions are that it takes a lot more effort and fiddling about to get the results that I want. Using Lightroom and Photoshop is like driving a Bentley to get from one place to another. Everything is comfortable, fast, smooth and easy. The Linux image editing tools I've used so far are more like driving a very basic small car (not naming brands here). It will get you to your destination too but you are going to feel the potholes more, you're going to have to top up the oil, the windscreen wipers aren't great...well I am sure you get my drift.
Sadly from a professional photography workflow point of view Linux is too cumbersome. It is possible to use and to generate high quality beautiful professional images. And I know that there are several professional photographers who use Linux applications exclusively. But for me the process is not slick enough and would harm productivity. So I remain enslaved to Windows.
However I am going to work with the Linux community and one day we will get there. I do prefer the OS (particularly Ubuntu) GUI. Open Office is superb and it does everything that I could possible want. All the other applications, surfing the net, music, video etc are excellent. The answer for me in the near future will be to run Windows and Linux side by side.
I will keep you posted on any further developments in my experiments with Linux. Please do contact me if you are a photographer using Open Source image editing programmes. I would very much like to hear about your experiences.