I filmed a short movie of my son on an iPad. Transfered it to my iPhone with MovieShare for iOS. Then I transfered it to my Mac mini using this desktop version. Easy.
For the reverse, you need to be moving/sharing m4v files that are formatted for the device. I sent a 300MB video to my iPad just fine. I separate m4v wouldn't transfer without conversion (apparently offered via app upgrade).
I am running OS X 10.7.5 on my mini, and the App worked fine. I tried it on my wife's aging 10.6.8 laptop, and I was getting crashes, so I suspect there is a OS version problem that a few people are experiencing.