Why learn MySQL?

I've been a DBA for SQL Server databases since 2003, but always wanted to learn MySQL.
There is something cool in the fact that it's Open Source. Well, "cool" is actually a nice definition, and also is the all time favorite "warm fuzzy feeling", but if you think about it, it breaks down into the following (at least for me):

From the DBA/Developer perspective:

• You know you have nothing to worry about when you're installing another server.
  
• All the features are available - you don't need to make sure that you have that Visual Studio Ultra-Duper edition with Super-Amazing addon license.
  
• The bug-tracking system is ugly, but it's there out in the open, the way things work is transparent and you really feel that you can contribute to the product (my first critical bug in MySQL!).
• You grow with the software - once something new is added, it's there, forever. You don't have the "Enterprise Edition vs Standard Edition" comparison tables.
• You get to learn the Linux ecosystem. For someone like me who came from the Windows world, this is a big plus.
  
• If you can do with Open Source what other people can do with proprietary - some of the arbitrage between the business cost of the two solutions goes your way.
  

From the Management/Business perspective:

• It's free.
• Really, it's free! The more servers you have, the more money you save. For example, one CPU (not core) license for SQL Server Enterprise is around $20,000.
  
• You get to say you're just like all the other Web 2.0 startups, and use MySQL. Hey, even the big mighty Google uses MySQL.
• It's free.
  

I'm ignoring the MySQL Enterprise offering, since the way i see it, it's really a support contract. You give money, and get a more orderly flow of version updates, some monitoring tools, and support. None of those you get when you pay for SQL Server or Oracle basic licenses.

In the next post - why not to learn MySQL.