Benchmarking that can be tricky for the same reason that benchmarking anything that reduces cache expiration can be tricky. If you reduce cache expiration your query might not benifit, but if you take a holistic approach to it and apply it to the whole database it'll benefit as a whole.
Any big MySQL powered application is likely to make wide use of this. Which goes to show that doing any benchmark comparisons between databases is often meaningless. You can't benchmark the same schema/queries between databases because they'll be optimized for the database you started out with.
Note that with this, you don't have to use unique indexes to indicate on-disk layout. Of course cluster needs to be run occasionally but it is far more capable.