I just recently read from a forum site that Paint.NET now can support PSD file format (albeit not all functions are available). I did test the plugin by extracting the dll file to the File Type folder of Paint.NET program. In deed I was able to save a design as PSD and was able to open the design on Photoshop without any mis-alignments or errors.

I was disappointed though that PSD files from the early Photoshop versions (version 7, I think ) where the only files that can open on Paint.NET without any errors.