There is free color management software at
ArgyllCMS.com (Windows, OSX and Linux).
Re Inkscape: There were lots of problems the first time I installed inkscape.
Now (version 0.46) there are a few things, you learn to stay away from to avoid program crashes. It can still crash but mostly it will save your current work automatically.
You'll have to install a few programs like ps2edit and image magick in order to use all the available formats.
It's really an awesome program. I also have Corel Draw ver. 8, but I never use it any more.
I make most of my work in Photoshop, but use Inkscape to create different object, that I assemble in Photoshop.
I am using GIMP for some special effects, but miss adjustment layers too much to drop Photoshop.
Edit: Adjustment layers is not the only thing I miss in GIMP.