Okay, as of 0.7.7 this is available, but not in the manner that lubar describes. I ended up needing to parse through some commit logs on git hub to figure this one out, but the following code does actually work for me now:
var io = require('socket.io').listen(server);
io.sockets.on('connection', function (socket) {
var address = socket.handshake.address;
console.log('New connection from ' + address.address + ':' + address.port);
});