Run away! This is terrible! Never use it! It's the worst thing ever... No. No it's not. Multisite is AWESOME. As long as you understand what you're getting into.
Multisite is a Bad Secret Keeper Logged in users are logged in for all sites User profiles are the same for all sites Changes to theme files are changed for all sites
It Can’t Do Everything Easily It’s not easy to share content or menus SubFolder sites have / blog/ in their URL Restricting plugins is complicated Creating special user roles is hard Moving it (or just one site off it) is tricksy