I have tried a variety of cameras. I just sold the last of them and have a Hero3 on order. At $199 with wifi, it's kind of a no-brainer. GoPro is pretty much the standard bearer - just watch a show like Mythbusters - they must buy GoPros by the crate, they stick them on everything from helmets to race cars to surfboards.

The most recent camera that I tested was a Sony HDR-AS15. The picture quality was pretty bad even at 1080p. It didn't look horrible when watching video but when you still frame it you realize that there's a ton of noise and compression artifacting, so you can't make out detail (like license plate numbers). In the still frame "interval" mode somehow it gets even worse - the photos are ridiculously noisy and little detail can be made out.

I used a Contour Roam before that - it's an OK camera but the complete lack of controls is a real problem - you can't change what mode it's in without plugging it into a PC and using some software (or as I did, editing a text file that's in the camera). The picture quality is OK on it and it's got a nice form factor. But it has no circular recording and no way on camera to erase photos, so you must plug it into a PC every day or two and erase the files.

I also used a Chinese/eBay "ExtremeCam" which was actually an excellent camera, had more features than any of the name brands I've used, and good photo quality. It's pretty large though. For frame mounting it'd be OK but on a helmet it was heavy and large.

I did keychain cameras (808 #16) before that, and while they had surprisingly good video for something that costs $40, the 20 minute battery life and lack of waterproofing really makes them not a good choice for this.

Once I get the Hero3 in and confirm that I like it (I will be surprised if I don't), I will order another for rear facing.

IMO, cut to the chase and order a Hero3 rather than wasting your money on half measures. I did the same stupid thing on lights - I kept buying various Cateye and Nashbar $30 lights until I finally gave up and spent $120 on a Magicshine. I easily spent $120 on useless lights, just as I have spent way more than the cost of a GoPro on trying out cheaper cameras.