We have just published Andrei's first version of the multi-threaded slave as a preview release.
Currently, the master produce a load by concurrent multiple client connections while the single slave thread execute replication events one by one. In some scenarios, this causes the slave to lag behind the master.
With the multi-threaded slave work, the replication slave will scale on multi-core machines.
This is a very early preview with serious limitations. Even so, please feel free to try it out and let us know what you think.