I use MySql for all my projects these days. In the past I've used both Sybase(when working at one of the big investment banks) and Informix(when working at one

I use MySql for all my projects these days. In the past I've used both Sybase(when working at one of the big investment banks) and Informix(when working at one of the worlds leading customer tracking systems) and postgres for a number of small person projects. My current project is a logging/reporting system which has between 50-75 million new rows per day amongst 2-3 tables in MySql with very few problems on a single Amazon EC2 instance(I've had to switch to partitioned tables for reporting recently though). My last employer did a tracking system with over 1 billion impressions a day on MySql with no problems(Multiple servers) Including near realtime reporting(delayed by about an hour). Thats my plus side for MySql. I really have no negatives for Postgres but I haven't used it much so I can't honestly report from either side. Others I am sure will be able to add more from that side of the argument.