as far as I'm aware, mysql's strength is in it's SELECT ability but INSERTS aren't as good. So it depends what you want to do with it

and it costs nothing

DB2 Universal Database 7.2
$20,000 per CPU (unlimited users)

Microsoft SQL Server 2000 SP2
$19,999 per CPU

MySQL 4.0
Free download; commercial license up to $200

Oracle9i Database
$40,000 per CPU (or $800 per named user)
What about SQL Servers shocking error rate?! 10%!!