Thought it was about time I joined up as I've been using Paint.net for a few months now.
I tend to use it for chromakeying out miniatures and models used in book cover art.
I took an off the shelf 1:18th scale Aston Martin DB7
Then used PDN chromekey option to isolate the model from background. Unfortunately I didn't get a good key due to poor lighting of the greenscreen so adjusted it all using Paint.net.
Then placed image onto background plate where various layers were used for lighting, grading, dust motion blur etc.
Only problem I found was that Paint kept crashing when using some of the effects options that were add-ons. Guessing either my old laptop is at fault or there's some corrupt script etc.