I plan on having a dev site these up, but: 1) What are the benefits? 2) Anything else I should know? I'm particularly wondering about below: To use this feature, you must generate your own IDs and be able to consistently associate them with a set of data. In a typical scenario, these IDs can be generated through your authentication system, passed to an account at sign-in, and then sent to Google Analytics.
You can find info here: https://support.google.com/analytics/answer/3123662 Has to do with session unification.