At that price, the camera can double as a HD camera as well, for general use as well as if my brothers or friends want to borrow it for skiing.
The device comes with the camera, a waterproof case (with both a waterproof backing and a non-waterproof backing), several adhesive mounts for attaching it to a motor-vehicle, as well as a helmet mount. Sadly enough, the device as is does not come with a scuba unit, though a scuba case can be bought separately through eye of mine for about $100.
The camera comes with a few modes, 720p, 960p, and 1080p. The default is the 960p, which is a weird mode which produces a square picture. The reason for this is that on a bike you might look up and down often and it could be useful to get more picture of road. Having tried it once (see sample video), I'm likely to stick with 1080p.
On the helmet, the camera does weigh your head down more. I'm not sure I would want to carry it up a major mountain pass on my head, though sticking it into your saddlebag (or jersey pocket) and mounting it for the descents seems like something eminently doable. (Uphill, I have no issues with manipulating a Canon S100.
The output of the video is huge. For 1.5 hours, it'll use up 8GB, so at least a 16GB card would be recommended for any kind of extended use. The battery will run out in 2.5 hours, so getting more than 16GB would be pretty pointless unless you have a spare battery. As for the lens quality, you can see it generates a lot of flare when pointed into the sun, so I would make a note of that. This is pretty bad, because cyclists don't usually have control over the flare or not. Note that the camera is designed for what I call "point and pray". Since there's no display for the image you're getting, and the camera's mounted on your helmet, you just can't possibly know what you're shooting until you get home.
On an unsupported tour, I'm not sure I would want to have this on my head or in my saddlebag. It weighs only 213 grams (without the charger), but since it uses up video pretty quickly, you'd either have to carry a stack of SD cards, or you'd have to carry some sort of additional storage, which would be even more weight. On a supported tour, however, such as the first half of our tour of the alps, I would consider it eminently usable. I am now extremely curious to see if I can get Pardo or some other fast descender to stick it on his helmet and take it down Page Mill Road or Highway 9.
For editing the video, unlike indoor videos, where lighting frequently demands color correction (meaning you pretty much need Adobe Premiere Elements or some other such software), outdoor videos don't need much color correction, and all the editing can be done with say, Windows Live Movie Maker, which is what I used for the above sample. The output will likely be huge, but with storage essentially free on YouTube, there's no reason not to store your video there and delete it from your hard drive afterwards.
Would I recommend this? I hesitate. First of all, video editing is much tougher than photo editing. It's not clear that I want to do it, or for that matter anyone else. Secondly, I've been very happy with my compact camera photos, and I'm not sure if video would help. On the other hand, I want to attach it to some of my friends' helmets so I can see how they descend, or get their comments on my descents as well, so in that sense it's a useful tool.
Ironically, the one place that the HD Hero would be most useful is actually for Scuba. The 2.5 hour battery life is just right for a 2-tank dive, and the fact that the Scuba case comes with a wrist attachment means that it won't get in the way, unlike the Canon underwater housing I've been using. Neutral buoyancy would also be a non-issue since it would be attached to you, and the case has essentially no air, unlike the Canon cases. I'll probably give it a shot and see. In the mean time, I see no reason to regret the decision at the price I got it for.