The S is almost certainly subtitles, as they used to carry an old school "Subtitles" tag top right (like you see on the idents) through most of the programming, but there is no actual requirement to subtitle any of BBC Parliament's output in the licence - the other BBC channels do (100%), but Parliament has 0% requirement.
Actually suits the channel quite well - better than its predecessors. I know Reith is divisive on here, but it's a clear improvement on Helvetica.
If I had to make one change, I'd take out the black 'event' box and add it to the bottom of the screen so it read '
HOUSE OF COMMONS
HOUSING QUESTIONS '. I'd also like to add a party ID tag, but I'm not sure where you'd put it.
The previous look used to have a ticker (like the BBC News design it held onto for months on end), so I presume the white bar is where the ticker will go when they decide/need to use one, unless they decide to go the full hog and make it a flipper. Time will tell.
You know my feeling on Reith but I have to say this, just yesterday I mentioned that the Reith rebrand was not yet completed, and then this happened today. Sometimes I feel that some of the folks at the Beeb are reading this forum
I think this looks good, the only thing which looks a little strange is the [S] tag at the top - it looks more like a technical error than an indicator really. I would suggest tucking it under the programme tag in the bottom right (if small then it won't clash with a flipper/ticker really).
The only other change I'd make is the colour on the date in the bottom right - grey on white isn't very legible at a distance - maybe a darker grey?
Overall, very nice, much better than the old set which had looked quite aged of late...
I presume the switch happened this morning - I note there was 5 hours of a US Congress Committee scheduled this morning (ending at 1pm) which would have been perfect cover for any technical switch over required...