One small idea:
Once the network traffic starts flowing, it's difficult to switch to the Javascript tab because it's constantly flowing off the screen. Maybe make the tabs fixed in place? Or have a check mark that can make them fixed or unfixed?
Very cool. You might be able to get some traction by using this to show some examples of common web vulnerabilities (just like this one) in the wild. I'd read a blog with those religiously. This was great.
Cool. I was just using ScreenFlow today to capture a video of a bug for my team. This would have saved me alot of time today. Just signed up for the beta!