I think Gavin should de-hitch his wagon from Mike Hearn after hearing how Mike proposed centralized checkpointing. The blacklisting thing was his one free pass at a really horrible idea. Now it just looks like he doesn't get what Bitcoin is really about.
I can see why Gavin would utilize XT as an end-run around the political gridlock in core, and I also see that Mike Hearn has a unique perspective and background that is useful, but he should not be a core committer in my opinion. Gavin is the only person qualified to (provisionally) lead the project as far as I can see now, but I think "palling around with Mike Hearn" will be viewed with suspicion, especially if it's unnecessary. Why not just just add in the patch to Core and fork off if necessary?
i too think that Gavin has to explicitly state that he will be the lead core dev for XT. i don't have as much of a problem as you seem to have with Hearn being a core dev for XT as long as Gavin has the last word. the other good thing is that Gavin can bring in a whole new core dev crew with more academic expertise with more of a like mind towards sound money, which is a big part with how i see these differences btwn Gavin and Greg.
the checkpoint thing Hearns was talking about was only if there were 2 persistent chains with XT being a minority. i don't think that will happen.