digikam/shofoto they support 16 bit colour depth and handle basic
adjustments and editing. I can manage B&W conversions fine as well. I
have GIMP on my system though it gets used more for graphics/logos than
photos and I have Picassa which I mean to play with some day. Krita is
the same though its not installed right now...try it some day.

I am not a CG artist so this works out fine for me. My wife has PS 4
because the student discounts made it attractive but that said she
plays with the toys more than i do.

she shoots digital Point and shoot with overrides by preference and I
shoot film and digital slr and occasionally a p&s because its the
camera I have at the time.

It occurs to me that I usually have the development version of gimp
installed rather than the stable from the repositories.