Database access is highly restricted with PIM. If you're using the cloud version, you probably won't have database access or a view of it. If you're wanting a customized application, you can develop the out-of-the-box PIM solution with a little bit of customization here and there without even needing a database. That's a very big drawback. As a developer or as an architect, you need to have a data model. I know some people use it without database access and the issue is that they don't know what that data model is built on other than just seeing it through UI tabs. The one thing I'd really like to see is for the solution to be made scalable.
