Well I am watching "999 Special: Diana's Legacy" which is from 1998.
The stream is only 225Kbps, but is extremly good nevertheless, the compression is excellent. There is no buffering whatsoever and had no problems using it, it just loaded up straight away.
Jumping/forwarding the stream also causes no problems and buffers in ~1 second.
So far, im pretty impressed.
The trial is just a taster too, there will be huge amounts more content when its actually launched!
Well done the BBC