A few have, but I'm not sure of the exact number. I also recall some leaving a year and a half or so before grid.org shut down due to frustration from the problems they were having at the time. David Wanat is one of those. He used to do statistics for us a grid.org. That's also when I first set up an account WCG.
As far as other former grid.org names, I think I recognize: fotokemist, The_Dentist (TBittner), LarryC (N7LUF), T.G. Wakko, Lighthouse, Hanski, Gottu, Sotty, littlepeaks, terryw46, designwebs. I'm sure I missed some.
There were a lot that didn't come over. After the team split at grid.org, a lot of those on the old Team Christians became silent. Most of the active forum users went over to CAC, ChristiansAgainstCancer. I miss quite a few on the old Team Christians, like simonedwards and others, even maggi. The grid.org shutdown was pretty sudden, so they may not have gotten the word in time... especially if the agent was on a forgotten cruncher. The UD website used to point people to WCG, among other places. But that now forwards to their new venture.