Dunno about pro's, but I played live against Ronnie O'Sullivan (snooker player?) in a casino cash game, and online I've played against a couple of footballers (Frank Lampard and Colin Hendry...different days!). Problem is, you never know if its the real people when its online poker, so I do take those two with a pinch of salt - although Lampard is a big gambler.
Missed out on a poker showcase in Manchester a few sundays ago with some of the Hendon Mob and I think Neil Channing. I was gutted, aside from Roland De-Wolfe he's my poker hero!