Gimp is ok if you do most of your work in camera, but it does feel like a slow younger brother with one big shoe for any kind of edit or manip. (>.<)
Have you considered PaintShop Pro ?(R400 ) Videos
supports 24BPP for HDR, dual monitor, RAW import
and has quite a few interesting features PS doesn't have (although I'm faithful to PS)
I'm not a big fan of Open Source for serious apps - It's the TFCD of the software world.