Using MySql at work, I just want to warn you about some weakness :

Error logging. It's especially difficult to know what wen wrong during an import.
Advanced SQL order. some useful features like sub-select are lacking in my version (not the latest although).
crash. unexpected RARE crash of the server occurs sometimes, with no data-loss/corruption, just restart the server and it's ok (I've read on the net that other site had similar behaviour)

BUT

Mysql is amazilgly FAST and easy to setup !(nothing compare to ORACLE or even Postgres...)
The Perl DBI interface to Mysql is simple and powerful (BTW shouldn't we state that any sentence with Perl and easy is a pleonasm ? ;-)