It's heavy, the servo placement is off, massive glitching from the frame, the list goes on and on. I'd have to go back and find the posts but there was a discussion about it a while back most likely on RCGroups or Run Ryder

I have heard nothing but good things about the CNC head they make. You can get it for cheaper from RC-Expert though and RC-Expert stocks all of the parts. Apparently that is a really good upgrade if your going to spend the money.

The E-Sky head just went through another revision. I've not seen the new version though which I believe is version 4. The blade looks like it was based off version 1 of the head. The version 2 head I believe was the first Bell-Hiller head. The version 3 head was the one we've all seen so many times. I've not seen pics of the version 4 head yet. That might be why the price went up.

Balsa Products looks to have most of the head parts in stock... I've ordered tons from them. Great company with fast shipping.
http://www.balsapr.com/view.asp?id=V019752