Hi,
I have been speed testing my Phantom 2 Vision. With no wind whatsoever it will go 40mph(64.37Kph). In a 10mph wind it will only go 30(48.28Kph)mph into the wind, but I got her up to 50mph(80.46Kph) with the wind at her back. My experience is that it takes 300-400 meters(yards) of full throttle to get it up to full speed.
[youtube]http://youtu.be/p5vsuPZVpts[/youtube]