Had to give Lulin a go. Toss of a coin. Do I guide on the stars and try to get the comet zooming past, or guide on the comet and let the stars whoosh by. I chose the latter. You'll see the comet dim towards the end. Dew started forming on the lens and that was pretty much the end of my night.
About 1.6MB animated gif. 20x3min shots.
http://piggo.com/~troy/photos/2009/2009_02_28/lulin.gif