The issue#166714 has been fixed but was not included in rc3 it's the cause of a lot of the performance regression, the issue#167399 hasn't been fixed yet.
These issues are a big deal for those projects with large code bases.
Jiri Kovalsky wrote:
* Regarding the other Nigel Leck's _performance degradation_ (#166714), it looks like we have fixed what was doable (2 out of 3 subproblems) and the remaining stuff (slow "Go to Type" _right after_ file modification) will have to wait for 6.8. We have some possible solution but it could potentially destabilize the other core functionality. :-\
