My developer brought up an interesting problem with Launch: on a slow network, he sometimes gets a flicker when a page is loading.
After numerous tests in Google Chrome where I throttled my network speed to "Slow 3G", I traced the problem to some Direct Calls _satellite.track() that are used in some rules' actions (implemented as custom code), i.e. there are rules inside Launch that include _satellite.track() themselves to other rules. When I blocked those min.js scripts in Chrome, the flicker problem went away.
The Direct Calls are used to call the actual Adobe Analytics page view beacon. In that same rule is an action to track an Adobe Target page load request. That action also enables body pre-hiding. And that caused the flicker. Disabling the pre-hiding "removed" the flicker.