I think 5.1 gets some bad press for not being a compelling upgrade. It's not the big features that make the difference, but the subtle ones. I wanted to highlight some of the these that may make your life easier when it's time to upgrade:
* Prepared statements can now use the query cache. BUG #735 * InnoDB auto_increment insertion is more scalable. Manual Page * The long_query_time can be set to values less than 1 second. BUG #6238 * SHOW PROFILES is available for everyone, not just community users! * Creating Triggers no longer requires the SUPER privilege.
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