I had it on a couple of shoots sitting in the video village.
Sometimes it was used as a playback device (before red epic had playback) and sometimes as an external recorder for F3.
It is a simple device,with only a couple of buttons, but yet there were always some problems with it.
Like once we couldn't get the output on the monitor except for playback. You look up in the manual, and you realize there is not much you can do. Manual says it should work. On the second day of the shoot it started working.
It has slow response on the buttons and you never know how hard you have to press them.
When you set it to start recording automatically when you hit rec on the camera it doesn't always work due to signal problems coming from the camera, or caused by the cables connected to HD SDI.
Sometimes it offers you to format your media in the middle of the shoot if there was a power failure.
All these problems, yet, I wouldn't mind owning it as it seems a nice little device for personal use.
For serious production I would never recommend it. Maybe I am wrong since there are so many of these around, and AJA is a reputable company. Dunno...
If you can get it cheaply go for it, the media u use with it is really cheap which is cool.