We never had a single issue with buffering or playback, and it was truly better than TV. It definitely felt like the future. I was really sorry our American friends in the USA couldn't experience the coverage like we had in the UK (without a VPN).
My only issue was with Flash. I'm not into bashing Flash just for the sake of it, but my only frustrations were caused by Flash just not living up to the rest of the delivery experience. I think it was the hardware acceleration issue that is already mentioned in their FAQ. Geting the video to play was sometimes a case of throw a 6 to start.
To my mind the mechanics of live streaming and streaming archived content are completely different and you usually have to wait ages for a live broadcast to be archived off for on-demand playback, yet the BBC somehow managed to blur the distinction. It might not be that difficult in reality but it was impressive to me.
There's some really interesting tidbits in there and he offers a candid perspective of how it went and the future of streaming TV, etc.