Correct me if I'm wrong but STM doesn't help you if your operations include side effects outside of STM (writing to disk, a database, the network)--exactly what async operations are usually used for. Aren't you back to locking at that point?
I don't understand the problem you're describing. If you're waiting on some external resource then you've yielded to another "thread" in either an event loop or green thread style. Are you suggesting partially modifying some state, then waiting on an external resource before finishing modifying the state? And no other "threads" can touch the state in the mean time? That is going to be a bad thing to do no matter what style you use.
Yes. My point is in the green (or native) thread style, it is not always obvious when you've stumbled into this situation (since you can't tell by looking at a function call whether it's going to yield at some point).
