The Windows Team blog announced XMPP compatibility with their MSN/Live IM network recently.
Have anyone tried to get iChat to work with MSN yet? (I'm not looking for Jabber transports)
No, it is not implemented yet.
In the meanwhile, you can use Cocoon for MSN chat as an iChat extension.
As Gerry said, Cocoon is your only option at the moment - but it hasn't been touched in months, despite continued donations from users.