Not sure how long this has been out, but after reinstalling (for the 3rd attempt) visual studio 2005 it prompted me to use windows update. However, on this site was an advert for Microsoft update which includes office, windows and more. (looks like the more includes beta software but that needs to be enabled under the change settings option)
All this seemed to do is download a new activex component, add an icon to my start menu and then take me back to a page called Microsoft update page - exceedingly similar to windows update in look and feel.
I've not seen this posted anywhere (but could have missed it) but it looks like this is the client that would go with the WSUS server
It's had quite a low profile launch. Tried it on 3 computers - works fine on two of them but no won't work at all on the other and I haven't yet worked out to roll back to Windows Update.