The last MySQL limitation to bite me was that time columns are truncated to whole-second granularity - no milliseconds or microseconds.

http://bugs.mysql.com/bug.php?id=8523

If you want sub-second granularity, the advice is to store milliseconds-since-epoch as a BIGINT and have your application convert it to a time:

http://feedblog.org/2007/05/26/why-doesnt-mysql-support-mill...