I tried MySQL again last year. After it insisted that an auto-incrementing integer field I had created be the Primary Key of the record, I dumped it (I mean it wouldn't let me designate any other field besides the auto-inc integer field as key). PostgreSQL still does everything I need, is free (as in free beer) and works perfectly for me. That plus PostGIS. And though I actually develop mainly in .Net I never touch MS SQLServer.