The big thing is at some point we're just at the mercy of the hardware and configuration. We've stripped out a bunch of queries from the older versions with the rewrite. Some places where it used to take 3 queries to get the info, we can now do with 1 query. However, that being said, whenever MySQL gets that many rows in the table it really will depend on hardware and configuration. You'll want to have a very tweaked mysql config file to make sure it's operating at it's best capacity with that large of a data set.
