[update - 3 April]
The comments to this entry (below) relate to an error I made in posting this article. When I first installed WSUS, there were no updates listed for Exchange or SQL (hence the earlier comment - done before the very long synch process). But after the first synch, they did in fact appear. This is possibly confusing to new admins, but understandable. Thus far, I've not seen any actual updates offered for these products, but I've been away a bit and have not had much testing time to put in. I would be very pleased to see Microsoft come out with more details on precisely how the applications (Exchange, etc) are to be handled.