If you're interested in trying gimp, check out Partha's latest build
here... It includes a lot of gimp scripts and plugins (my fave being g'mic) and most notably in this 2.8.4 release from Partha, includes a port of v.19 of ufraw... (ufraw was broken with 64-bit Windows for a while but it's back with this...) So if you drag a raw file into gimp, it will open in ufraw first for 16-bit adjustments and then export into gimp for 8-bit edits from there.. (Just also note that there is a known bug where if you resize the ufraw window after opening the file, it will crash, so just maximize the window and leave it alone after that).. If you have a beefy system and want/need to do 16-bit editing, I also recommend Partha's 2.9 build of gimp. (Use the portable compile so it's self contained..) 2.9 allows you to edit straight in 16-bit using gimp..
Also... if you're into working in LAB, Delaboratory is available on Partha's site, and it's awesome too... 16-bit editor and exports into gimp
Rawtherapee is great and free too, and from what I saw with darktable from the link above, is very similar... I use it quite a bit and it exports to gimp too..