video super fast. The lag you are seeing is actually the delay in video from the iPhone, and not the remote touch. VGA and HDMI adaptors use Apple's high speed digital DisplayPort protocol, which has virtually no lag. If you have no choice but to use composite video in you system you will find that if you use a HDMI-to-Composite, or a VGA-to-composite you will be back up to speed again. You will also get better image quality, not HDMI by all means but better than the standard iPhone composite output. Composite is acceptable for general in-car use, if you want to smash angry birds while driving I suggest using HDMI output
Foster182 (video above) is running HDMI directly to the monitor. You should see there is a big performance difference. Also, VegasNate didn't calibrate his screen properly (you can see the touch point is off) which makes it look slower than it actually is.
Hope this helps.