Taking time out from the Big Migration job to share
this with you, and before you say anything *I Know* this is old news, but forgive me because I've been away from MySQL for 4 years, and just because you know this doesn't mean that there aren't other "late adopters" like me out there.
Over the past few weeks I've come across quite a few posts on the net from folks who wanted to use oracle style links between MySQL databases (I don't need to, I just spoted a theme). Researching the storage engines in Mysql 5 (we're upgrading as well as migrating) it seems there is now an answer in the form of the Federated storage engine.
The article also provided me an answer for the perennial problem of needing several instances of MySQL in dev and test, often for exactly the task currently at hand, migrating from one version to another, that answer is the
mysql sandbox. Neat. Its a shame that I've already set up my dev environment, I'd like to play with that.