Thanks James.
True about discrete channels being very prominent nowadays but with Logic 7 also able to expand 5.1 to 7.1 and with 5.1 being the overwhelming majority of audio tracks on DVD's, Blu-ray, tv, SACD and DVD-Audio, etc. having another alternative to extract rear channels would be a nice alternative to see in a Bryston product along with more flexibility in the center channel but I can understand not wanting to devote the time/expense in integrating the L7 modes.
For 3.0/3.1 L7 can extract surround data (2 or 4 surround channels) when I'm pretty sure PLIIx can't and with 4.0/4.1 L7 can extract a center whereas again I don't think PLIIx can. PLIIx like L7 could extract rear surrounds from a 4.0/4.1 mix though. L7 can also extract a center from a 5.1/7.1 source in which there is no content in the center channel due to the intent of creating a phantom image by taking info from the main L/R speakers, again I don't believe PLIIx can do this either.
For stereo sources L7 provides a level of surround steering not offered by Dolby or dts and even with discrete 5.1/7.1 sources, with L7's adjustments if you are watching a movie with very little surround information you can steer out surround info from the main channels into the surrounds (again 2 or 4 surround channels depending on the users setup) to give a more immersive experience.