There isn't much more to say about the files themseleves.

nerd has a tutorial for how to inject new morphs from them.
There's similar information in sixus1's forums

kuroyume0161 has a utility, MorphExchange, for converting them into morphs in a CR2.

Most apps that interoperate with Poser files don't get on with them, and so require having the option to save them turned off.