The ones that I'm aware of are:
Andrew McKinlay - James Taylor Quartet
Dave Swift - Jools Holland
Joe Hubbard - 80's session giant
Jimmy Sims - Saturdays/Mika
Rob Burns - 80's session giant
Guy Pratt - Pink Floyd
Ed Hetherton - Elliot Minor
Janek Gwisdala and Steve Lawson occasionally show up to promote something.
I know Randy Hope Taylor, Nick Fyffe, Paul Turner and Lee Sklar have browsed but not joined, I strongly suspect Mark King is aware of the site. Any others haven't made themselves known.
The pros I've conversed with find forums threatening and overwhelming, especially with how arguments tend to escalate out of all proportion. Sometimes I have my work cut out trying to persuade them that this isn't always the case.