I like Oracle's product. It's reliable, and very fast. You can find people who've been using it for a long time and understand how to get the last ounce of performance from your database. Unlike some of the OSS database engines, you don't get halfway into a project and find you can't index dates, or some certain kind of query is slow and there's no way around it.

That said, dealing with Oracle the company is painful, and I wouldn't do it if I were by myself or running a small shop. Fortunately, I work for BigCo, and we have People who do that sort of thing. By the time it gets to me all the business stuff is worked out, the database is installed, and I'm getting an email with my account information.