Open Source Software - What Are Some of Your Biggest Learnings?

Mater mus, given its open source, and you have all these pluggings, can change whatever you can. Do you charge per user toobut? I gues it'll be very hard to do that if yourself hosts an option. What are some of your biggest learnings? Some things that you wish some one had told you early on, before you got started as open sor new open so fonde.