First of all, SUS rocks. But it doesn't "Push" the updates to the client, the server broadcasts that the updates are available to the clients, and THEN they go and download/install from the server. I just had to clear that up for those of you who think they get "pushed" to the clients.
If you want to "Push" them to the clients, I suggest Systems Management Server (SMS) from M$ or ZENworks from Novell. They can do what SUS cannot, but cost money, whereas SUS is free.