In reply to Michael.

If you use different Jetpack modules, each one of them will indeed have an effect on your site's loading speed - much like different plugins would. It's up to you to determine if the modules are worth the additional resources required. And you can always disable the ones that you don’t want to use.

It’s also worth noting that Jetpack does run some additional functions when you’re logged in. One example is the Stats module, which will run some additional queries to get information about Stats on every page load. Your readers, however, won't trigger this extra query. So, P3 could show inflated results. I would consequently recommend that you run the P3 plugin in a different browser or in an incognito window, where you won't be logged in.

I’m excited to hear about this project and I’m looking forward to finding additional ways we can improve Jetpack!