Performance Schema (P_S) has been available since MySQL 5.5, more than 4 years ago. It is still difficult to see production servers with P_S enabled, even with MySQL 5.6 where the feature is enabled by default. There have been several complaints like the overhead, that the fix is a work in progress, and the ease of use. 52 tables to query and 31 configuration variables is enough to scare people.
There is a solution for the second problem, the usability. It’s name is “sys schema“. It is a collection of views, functions and procedures to make P_S more user friendly.