I'm thinking of working on fixing Mono's Dictionary to be thread-safe.
It seems ironic: I wrote a large part of that Wiki page, and I'm in large part responsible for the dictionary code not being thread-safe. "Blame" me for the use of the move-to-front heurstic in the dictionary code, and I must say, it was a beautiful piece of code: see how simple it made the 'Remove()' code.
Of course I've disliked threads all along, and this gives me more reasons to blame threads for the ugliness they bring into the world.