The update today was to fix a problem with particle systems appearing as red X's in older replays/demos.
It looks like the update is necessary for dedicated servers, too. We're going to release an update soon that will require all dedicated servers to update. You might as well go ahead and update now to get the new binaries. The next update we're going to release will only include a new steam.inf file with an updated version number.
Sorry for the inconvenience.
-Eric