I've been a Calibre user for a number of years; just now joining the forum because the new version is sufficiently different that I am having problems with its internal reader.
I am using an original Nook Color, but with an N2A add-on chip (Nook to Android), so it has a double-boot option (Nook or Android), and I just always boot Android because it's more versatile. Consquently, I use the Android Kindle app, and convert all my books to the .mobi format.
I live in the Dallas metroplex area, and I am a happily retired, former computer programmer/analyst.