I've been to the Worlds event in Anaheim, as that's the only one close enough. I only competed in the Last Chance Qualifiers, however, and quit after Round 4 because it was getting too late at night and I needed my sleep. I didn't see any artists there or anything, but there was framed artwork of some then-upcoming cards. It's a shame they were simply prints, but I guess it can't be helped that nearly all of the illustrators have gone digital.
Obviously, I got no invitation...I rarely attend the tournaments. The only ones I went to this year were the Pasadena Regionals and Lancaster Battle Roads.