Whenever you click "Create Game", you start up a server which will then show up on the list for everyone to join. So whenever someone feels like playing, there will be a server, even if it's their own.
As for switching to 3.6.10, that's done in the launcher by selecting an executable that is designated as a 3.6.10-based build. Is it worth it? Depends. If you like pretty graphics, then yes it is. If you like gaining score, then no it isn't, because score won't save on 3.6.10 until the final version is out, and that could take some time yet.