Just had a play with local streaming of a live HD channel into a PC browser, worked fine but the "Transcoder state" page of the boxes web-interface showed that 1 transcoder was in use, so I presume it is rendering on the fly to distribute the picture. I presume that means it ends up being non-HD, but for the use-cases I'm thinking of (keeping half an eye on a sporting event whilst cooking tea, watching the news etc) I doubt that would be an issue anyway. Will be interesting to see what the quality looks like when it is deliverd via an app interface.
Two browser windows could simultaneously stream but a third couldn't start the transcoder, so I guess that would be a limitation with devices around the house.
Not likely to be an issue in practice though.