[vessenes]

The typical solidity dev is "but mutexes cost so much gas!"

There's an optimization problem not yet sorted out here. If I were king of ethereum, (happily I'm not), I'd make a very cheap mutex support part of the eth vm and encourage solidity and serpent devs to use it as needed.

[drcode]

I suspect we'll see something like mutexes in the next ethereum EVM revision.

[vessenes]

Yes, that would be a kind and fine thing to do, or at least change the cost of a specially designated bool argument to something cheap. You get one per contract, kind of thing. Or you pay on deployment.