I've only done two short flights so far. My experience thus far is not encouraging, but I'll spend some time tweaking to see if it improves. I'm in a rural area with very little interference.
With my android phone (Moto X), the DJI-vision software is utter garbage. The live feed works fine when I'm in my house, but as soon as I start flying it breaks up and the image freezes. When I get a chance I'll try again with my Nexus 7 tablet, and Nexus 5 phone. I'd say the usable range was maybe 3 feet. Or less. Effectively non-functional.
I tried an old iPod Touch that I keep in my car, and the experience was quite a bit better (aside from logging in to DJI, which was tricky since the 'login' button is almost invisible on the smaller screen). The video streamed smoothly, but it had serious lag that makes it useless for "real-time" FPV. Furthest distance was about 500 feet, and the video feed was lagging about 10 seconds behind real-time. So it was passable, but not what I was hoping for.
I'll hopefully get a chance to experiment using my wife's iPhone 5. Maybe the lag is due to decode problems on the iPod? A newer iPod Touch might also work better. I also haven't experimented with adjusting the stream quality. I think I had it on 15fps.