Testing this now. One issue for me is that I get a lot of traffic from reddit, stumbleupon, etc.. these users don't stick around for more than 5 secs and they are going to use up my captures quickly. I would suggest only counting captures that have clicks.
Another suggestion: I'd love to be able to see how users browse a particular page, but i might have to wade through a ton of captures to do so. Would be cool if you captured every user session and I could then search to find some that include that page, then unlock those session by using some of my purchased credits.
EDIT: One problem I'm seeing is that when the user goes to a new page the timer freezes and it takes about 10 seconds to start playing again, but it jumps 10 seconds ahead, so you miss some activity there. Looks like th is is because my website takes awhile to finish loading (lots of images below the fold).