I'm interested in doing some video while riding several rollercoasters (from moderate to intense). Does anyone know if the Canon VIXIA HF G10 or HFS-21 can handle the occasional jerking motions without messing up the internals?

Be careful, many places don't like you videotaping roller coasters. Last time I tried, I hid the camcorder until we left the station. I get the camcorder out and turn it on as we get to the base of the first hill. They turned off the chain that lifts the coaster up the hill. I thought it was just a normal feature. It wasn't They spotted me using the remote cameras. They walked over to me and confiscated my camcorder. Nothing happened to it, but it was a cheap camera. I don't know if I'd like them to confiscate a $2000 camcorder.

On tape based cameras, which I've used on roller coasters for many years, you do get some head bump, where the tape lifts off the heads and makes life difficult - although it's far worse when you mount the camera onto the coaster with a solid mount - hand held is usually fine - BUT you are talking solid state cameras - no problems at all - they might wobble a bit, but there are no moving parts to damage. If you contact them in advance and inform them you will be hand-holding the camera and will use a safety lanyard to prevent it falling - they'll usually grant permission. All they're really worried about is you dropping it over the edge and hurting someone.

Thanks for the tips!