I recently bought one and thought I would share my experience with it.
Main purpose in buying was for my 2nd cam person. She had been having trouble focusing our FX1's and now with GH2's I was worried. I had looked at the offerings from Small HD and others but just couldn't get my head around the cost....especially since my primary goal was focus assist. When the Sony model came out I looked at it a while then finally decided to buy it. I got it from Amazon for $399....figuring I could return it if it was junk or keep it if it was nice. Turns out it was a little of both.
First thing to note is that it does not come with any means to power it. You're on your own. I went to Batteries Plus and bought a 3000 mAh battery and charger for about $50. I have run the monitor for as long as 4-5 hours and have not had it die. I haven't tested to see how long it will run.
It arrived the same day I had a dance recital so my first test was also a working test.
First thing I noticed as I was setting it up was the colors. They looked amazing on the monitor.....except for the reds. The stage curtains were that nice deep shade of red.....but on the monitor they were brown. No manner of adjustment could make them red. I spent an hour or more tinkering with it before giving up and adjusting it so all the colors but the reds looked good.
Peaking worked really well.....and there is also a pixel magnification function that zooms in on the picture to help with focus. I haven't really used that function as the peaking works very well.
The fold up lens hood is also nice. Works well in most outdoor situations....though if you get the sun to your back forget it. The screen is reflective so that is a small problem outdoors....but not a deal breaker.
After some reading on the internet concerning the reds, I decided to return it for a new one. The couple of reviews that were out seemed to not have a problem with the reds. One nice thing about the return was the price was now lower....$322.00!
The new one arrived and I had the opportunity to use it again at the same venue. The reds were MUCH better....though still slightly leaning towards brown. The consensus of those I have talked to seems to be that you can't expect perfection at that price.
All in all I am happy with it. My 2nd shooter doesn't have any problems with focus now, and that is the main reason I bought it. If you need critical color I don't think I would recommend it. If you need focus assist and just want to have something bigger to look at then it works.
Would I buy one again?? Matter of fact I did. I liked it so much I bought another for my cam.

Mark