Like mosen I'm also using darktable on linux. If you are not on Linux, there is in the meantime also a build for Windows. I think it isn't that complex, if you are using the easier modules at the beginning. If you invest some time darktable is VERY mighty, especially when you are working with parametric masks. There is also rawtherapee, which I use for special tasks. But I fear rawtherapee is even more complex. Without some patience and a training period it's hard to get the best out of your pics.