A range of 3900' in my book is getting robbed of your freedom of the sky, but that's me. That's exactly the range I got with my P4 and GL300C controller (custom quiet ch, 4mbps). The problem is my P3P with (GL300A) was always going 2 to 3 miles with a windsurfer. For months I didn't fly my P4 because of it's poor range. Then I linked a GL658A Inspire controller to my P4 craft. Now it can easily go 2+miles, and I've gone over 3 miles in quiet areas. I don't feel I'm a distance junkie, but I certainly like the freedom of going somewhere without worry of a weak signal. Ocu-Sync? I'm in, if it's really got a better range.
I've learned not to believe DJI marketing hype. Remember the P4 hype.... 28min? 3.1mi? NOT ! It's more like 21min and <1mi using a stock GL300C controller.
I still love the DJI products, the best!