You know I dont' even think Valve has thought of this idea. What if when you turn on your computer for the day that it checks to see if a new version is out.
If so then notify the user with a dialog box stating that a newer version is out and "Do you wish to install it now?" prompt. This way if they know that there are servers out there that have not upgraded yet they can still play and wait later when they are not in the mood.
This also takes in to account that what if Valve releases a bad patch. Then everyone is screwed and can't play until the next patch fixes the patch.