I also work on large mysql instances (100+ million row tables and such) and just have to say innodb is not always the answer one would hope. While I do like it in favor of myisam, you can still run into pretty serious limitations... like deadlocks in insert only scenarios (actually they are pretty bad in general, but that perticular one is just magically bad) At my $dayjob, we actually had a client recently convert back to myisam because of performance issues with innodb. I'd like to recommend innodb in all cases, but due to the quirks of how mysql interacts with its table engines, you just can't.