(or at least some ideas)
I really enjoyed David Shrewsbury's presentation about Drizzle replication today at the MySQL conf 2011. It's not that Drizzle replication is fully fleshed out, but it sure seems like it's got all the necessary components to make it dramatically better than stock MySQL replication, at least from the HA perspective.
Here's some things that Drizzle replication (or MySQL replication, for that matter) needs for me to be able to improve on the Master HA technique that is used at Yahoo: