I don't use the OM-D for video. The OM-D does not natively have external audio input, but they do sell the Microphone Set 1, which adds an external audio jack by utilizing the accessory port on the hotshoe. I have not used it, but it's worth a look if you already own the OM-D.
The GH3, though, is the real m4/3 video powerhouse...all your audio needs built in and probably the best video in an interchangeable lens camera outside of dedicated video units.
Thanks for the feedback Jman. I am considering a move into m4/3 and have been leaning toward the Oly, but I'm certainly not locked. Video will likely be a small part of what I do but it could grow.
Without doubt, my challenge has been to determine the best system for me. There are some very good options it seems. Olympus, Panasonic, Fuji, etc.
The nice thing about m4/3 is that if you prefer an OM-D for stills, you can get a GH3 for video work too and use all the same lenses. Especially lately, it seems that the two OEM m4/3 manufacturers are really complementing themselves well with new lenses...Olympus brings out some great compact primes...Panasonic adds high quality f/2.8 zooms and soon to add some faster longer glass and ultra-fast portrait prime.
The OM-D does not natively have external audio input, but they do sell the Microphone Set 1, which adds an external audio jack by utilizing the accessory port on the hotshoe. I have not used it, but it's worth a look if you already own the OM-D. 
Especially lately, it seems that the two OEM m4/3 manufacturers are really complementing themselves well with new lenses...Olympus brings out some great compact primes...Panasonic adds high quality f/2.8 zooms and soon to add some faster longer glass and ultra-fast portrait prime.