I have a chin mount.
Only downside to my mount is that the straps on my mounting hardware keep my visor open a crack.
Upside, the straps keep my visor open a crack, since the vents on my helmet are more decorative than useful, I have to anyway. It adds a bit of wind noise in the helmet but my mic seems to get less wind noise the closer to the visor it is.
I just ordered a Rode Dead Kitten, I'm going to rig it to fit my mic, it should fit over the width fine, but I may have to cable tie the opening around the stem.
In the first image is the mount, I have it moved down a bit...it does very occaisonally shift, but it's easy to recenter and it bothers me as soon as it does but the difference in viewpoint is minimal. The mic cable and the GoPro adapter are held behind the mount plate, which is the main cause of any shifting, but a tradeoff I'm willing to make to avoid lose cable lengths.
Second image, you can see how the straps actually hold my mic in place, and provide a little bit of extra wind protection. I could probably come up with a simpler mount with a simpler lavalier mic, but I really really like stereo recording.
Now that I look at it, I might actually have the vents open which could actually be causing me some wind noise problems (not that I have a huge problem as it is). Double checking that once I get my deadkitten, plus throwing on the deadkitten will probably really improve my sound.
Once I figure out how to mount everything, I'm looking into a standalone recorder that records 4 channels, I wouldn't mind getting some mics mounted to the rear of the bike to capture everything behind me and trying for a surround mix. Of course, that's going to only be for me, since YouTube does not support surround (though I might be able to sneak a prologic II mix or something).