The only difference (they told me at Sam Ash) between the R16 and the R24 are the amount of channels. The electronics aren't necessarily better in the R24. You're still only limited to recording 8-tracks at a time.
But I started this thread some time ago detailing what I've been doing with my R16, after some people have emailed me about how good my videos sounded, here:
http://drummerworld.com/forums/showthread.php?t=69369
Suffice it to say, the R16 is only to record the audio. I use a Kodak Zi8 flash camcorder to record the HD video, and do both at the same time. I start the video, then roll the R16 to record the audio and do it all live. After the audio mixdown, I then take both files (audio file and video file) and dump them into iMovie on my Mac. I sync the two up together and there you have it!
Sorry to disappoint, but this is the only way on a budget that I could produce the videos I've put up on YouTube. I still use the computer, but only after the work is all done, so the computer doesn't have to be all that powerful, because you're basically just putting the two files together and uploading. But the results are much better than trying to record everything into the camera - alot of those cheap flash camcorders do not have a LINE IN jack, or when they do, they distort.
That said, the new Zoom Q3HD is intriguing because it shoots HD video, AND has a LINE IN jack. If it's anything like their other audio recorders, it should be able to handle the stereo signal off of a mixing console easy. I use my Zoom H2 (a two-track audio flash recorder) to record directly off the console sometimes.