The case for Polyglot Persistence was made throughout the day by several of the speakers. Most people seemed to acknowledge the fact that it is very likely one database may not have all of the tools you need to get your job done. Instead of coercing a single database to try and do things it was never designed to do, it is becoming more common for applications to use multiple databases, utilizing each for their respective strengths. But, of course, using multiple databases in a single application comes with its own set of issues, and you should make sure there is a real need for Polyglot Persistence before making that leap.
Thank you very much to the WindyCityDB organizers for putting on such a great event. I had a great time, learned a ton, met some interesting people, and participated in some great conversations. What more can you ask for in a tech conference?