Have you tried if renaming .m4v to .mp4 will fool WDTV to understand they are the regular MPEG-4 files?
M4V files work fine with a current WDTV Live device. When I had the original one, I did need to rename .m4v files to .mp4.
I also just found out that the Mavericks OS seems to have fixed a file sharing problem which prevented the WDTV from being able to read shared folders on Macs running Lion and Mountain Lion.
Awesome, that's what I was really hoping for. Thanks
Another thing I just thought of, does it read from a Mac osx journaled hdd? Otherwise I think I'll have to use FAT, but some of my movies are over 4GB. I've never tried those apps that allow a Mac to write to NTSF.
Yes, Mac formatted drives work fine with the WDTV. Are you planning to attach the drive directly to the WDTV rather than sharing the files over the network? Either way, you shouldn't have a problem.