MySQL probably is the lowest common denominator for a RDBMS in the webhosting world - you can't leave /home without it. This blog wouldn't exist without MySQL (someday WordPress will be database-independent). Sometimes I hear people say MySQL isn't a real RDBMS, or that it lacks certain features that causes it to suck™. I work extensively with MySQL and there are times when I wish for stuff like referential integrity (available with InnoDB tables, but most hosts don't provide it) so I don't have to code constraint checks in the application. I wish for transactions (again supported by InnoDB). I wish for a PL/SQL equivalent.
Now, these guys, they've got MySQL gotchas and an anti-MySQL list listing some niggly inconsistencies and general bad behavior in MySQL. And after reading that, I'll never trust what MySQL does to my data again (silently change my data would you, mysqld?).
(Yes, the entry title is grammatically incorrect on purpose.)