Here is a video from VIR using HTL with iPhone4.
At times i did run into issues with HTL. The video, overlayed map and sound were not synced and they were all at different points.
I would suggest remove all your music from your iphone to maximize available storage capacity. Turn off notifications so it wont interrupt the recording, and tell your friends not to call or text you
I couldnt use HTL in Summit Point last week, for some reason it was crashing or getting interrupted all the time, very annoying.
I have the iPhone5 now but cant test it since the RAM mount hasnt come up with the holder for iphone5.