Ask HN: How can I use one computer to manage 2 iPhones with iTunes 9?

I have a 3GS and my wife has a 3G. Previously with earlier versions of iTunes, it was possible to manage two iPhones on one installation of iTunes. I'm not even talking about anything more advanced than just editing a playlist. Somehow in iTunes 9, this doesn't seem to work anymore.

Also, I want to be able to manage my 3GS at home and at work, cause sometimes you have just have to change a playlist. This doesn't seem to work either.

Either I'm doing something wrong, or Apple is taking Big Brother to a whole new level.