Is Core Data Slow
If Core Data is slow, then you are most likely (1) using a very big data set or (2) not correctly using the framework. The latter is the most common issue. Core Data was designed with speed and efficiency in mind. It only fetches the data your application needs and fills in the gaps as your application asks for more data.
Unless you are working with a very big data set, I wouldn't worry about performance. Should you run into performance issues, then it's time to take a close look at how your application is using the framework.