Doc, seriously, crap or get off the pot, lol! The Mango release is fantastic!
To answer about Facebook chat, it has been pretty awesome... well, as awesome as FB chat can get given its own unreliable nature. In other words, it works great, but it's only as dependable as the other person's ability to stay connected if they're navigating the site. But I only use it for short times, because I'm too afraid of draining my battery (I should actually test it sometime).