I purchased two Hero Wide cams a couple of weeks ago, and mounted them on a small yacht in order to capture onboard footage from the annual Round The Island Race. I had no previous experience of using the cameras, or any similar products, but got good results immediately. There is no way to review captured footage on the fly - the camera has to be connected to your computer or TV in order to play it back - but I found that I'd got good results just from using intuition about where to position and aim each camera.
As other people have mentioned, the relatively small file size that can be accomodated restricts footage to a total duration of just under an hour per 2GB SD card, but swapping cards was easy. Battery life was not an issue - each camera filmed for around 2 hours, on and off, and the batteries still had life left in them at the end. However, I was using Energiser Lithium batteries, which the manufacturers firmly recommend.
The cameras have been, for me at least, plug and play both on my IBM laptop and my MacBook Pro - no special software, plug-ins, etc required.
The product doesn't quite get 5 stars for a couple of reasons. First, the audio is so muffled as to be virtually non-existent. A manufacturer-endorsed workaround is to drill a hole in the waterproof casing - not recommended for surfing or sailing! Possibly viable for motorsports - but maybe wind noise would be an issue. Second, you need to work overtime on keeping the waterproof casing in front of the lens as clean as possible - at one stage, one of my camera casings receives a thumbrint which is very visible on the captured footage.
Finally - and this is no fault of the camera's - the footage, while of good quality and clarity when played back on a computer screen, involves mammoth file sizes. Don't expect to publish to YouTube or a blog at anything like that quality. That said, streamed quality over the web is acceptable.