This courtesy of PS3 Fanboy:
Did you hear? The Home open beta starts today. The client has been patched up to version 1.03 and the servers are down while Sony does various jiggerypokery behind the scenes. TedTheDog states that the service should be back up, along with the launch of open beta, "early PM UK time," though he adds that he can't be more specific than that, thanks to the nature of the global updates.
Ted also confirms that the Home icon will appear on the XMB as soon as the final switch is pulled, though people who are using their PS3s at the time will need to restart. In case you're wondering, it's already past Midday in the UK, so it could go live at any minute. We'll update this post as soon as that happens.