I have been looking at – and listening to – their website here:
At any given time there is one concert which you can both view and listen to. So far the calibre of performances (in the musical sense) is very high. I tried this out on various computers for performance (in the computing sense) and synchronicity between sound and vision – watching percussion is a particularly good test of this.
On a wireless laptop the streaming didn’t really work at all first time, but revisiting it now it has improved. However, there’s still a bit of time lag between sound and vision; unlike the real world, you hear the notes before you see them played. The same problem with synchronicity appeared when I looked at the site over a (wired) broadband link. On a LAN there was no problem.