At least File::MimeInfo and my module already support filehandles and in-memory streams as well, so that part is covered. I like the idea of leaving File:: out, as it shortens the module name.
Personally, I've stopped trying to create "generic" modules together with the first implementation, as normally it turned out that my first implementation remained the only implementation and no plugins or other drivers turned up. But using MIME::Detect as the API class and leaving the door open for others to add backends sounds good.
