maybe its just you because ever since switching to a macbook and missing sync, my mogul and macbook work seamlessly together. i believe the m4a issue is a problem with iTunes. my friend tried to copy some music from his iTunes to my flash drive and it came up as m4a files. i believe that is the format when you download music from iTunes.
i personally download my mp3s elsewhere so they stay as mp3 files and have no problems dragging and dropping to my mogul.
the bluetooth PAN works without a hitch and is SO much easier then on a windows pc.
might want to look into an app called "Salling Clicker". it basically lets you use your mogul as a sweet ass remote via bluetooth.
mogul + macbook =