Mango has a lot going for it. But one "non-feature" is that it can easily take from 30 to 180 seconds to switch from one screen to another (i.e. Events Handlers to System Settings). Is there anything that can be reasonable done to speed this type of switch?
How to speed up changes between screens
I would check to make sure that you are using Oracle JDK rather than OpenJDK. Mango will work with OpenJDK but I've noticed that things run slow. The speed of your database and how many data points & events you have in the database can have an affect as well.
We are planning to release Mango 3.0 in the next couple months that will have a whole new UI which is much faster and offer many more features. We should have a preview of this soon.