Frank,
I watched the video again and thats true, only the takeoffs were instables.
I also noticed that there was a XBee in your quad. Are you using XBee to control the quad either?
What controller are you using?
I made a controller myself and I'm gonna try in the quad. It's motion sensitive. I posted in this topic: http://arduino.cc/forum/index.php/topic,65685.0.html
And I'm aware of the XBee range and Ill get a XBee pro. (up to 1.6km) Thanks for the tip anyway 