Hi Eric. Couple of points. XCF has been available as Gimp's native format for some time now. It's only in the latest versions that you have been forced to save in that format, other formats being exported. You can also export a tiff with layers, if you want to keep the layer information.
As I think I've said before, the 16 bit issue isn't really as important as sometimes stated in a lot of "real world" situations, where most "final" images are either jpg which is 8 bit, or print. The stage where big changes such as shadow recovery are made which could cause degradation such as "banding" are done in the converter with the original raw file at (for instance) 14 bit.
If you haven't looked at RawTherapee for a while it now has gradients and vignettes, as well as many other improvements. It handles CA and fringing very well. It doesn't (yet) have the retouching / editing abilities of LR.
It's all a matter of choice though, and what you are used to using etc.