Hi, I'm a newbie to paint.net (recent convert from GIMP) and the forums and came across this tutorial. Its the first one I used to get HDR type effects and gave me the desired results so I like it! Only thing I would change is to recommend that people only merge the layers at the final step. It you do the conversions on each layer then have then all viewable you can see what the final image will look like and continue to tweak each layer until you are happy then merge them into the final image.
I have found something weird though. If I merge the middle layer to the bottom then the top layer after, the result is as expected. If I merge the top and middle layers first then add the bottom it turns out quite different. Not sure why though.