My first reaction to MySQL was that traditional databases cost money for a reason.

The more that I have used MySQL the more I find I like it although FK support, poor subquery support, lack of stored procedure support or triggers are draw backs.

However, MySQL was originally designed as an extremely fast output database for simple web applications and if you look at it from that perspective then it excels.

My first MySQL project involved using the http://www.x-cart.com shopping cart and for this appplication it was brilliant.

I think you have to look at any database system in the context of what it is designed to do and MySQL fits its niche brilliantly.

POSTGRES is interesting because it looks to be an open source ORACLE clone.