Best instant messaging protocol?

http://en.wikipedia.org/wiki/Comparison_of_instant_messaging_protocols

Personally i prefer XMPP – lots of tools/features and easy to get going.

while I agree with seek2be, what’s important for us may not be as much of an issue for you, and for most people the deciding “feature” between IM protocols is “what are my friends already using?” (or, at worst, “what can I convince everyone else to use?”)

That said, if you are starting fresh, I’d argue for something open, like XMPP (Jabber). Many desktop clients already include support for it, it includes transport layer security, and you have the option of running your own server, if you don’t want to share your conversations with some faceless, multi-national corporation with questionable motivations (Lucy: “It’s run by a big eastern syndicate, you know.”)