And just before SP1....
The update is live at:
Please allow an hour or two for replication to complete between the download servers.
It will also be offered via Microsoft Update.
A request has been made to publish the KB. It should be live soon.
Hmmmm, I couldn't help noticing that as soon as RU5 was installed on our Hub Transport server in test and production it stopped all the services from starting up.
I think I'd advise leaving it a a while until these issues have been sorted out.