If you have any performance regressions with 3.5 we would like to know about it.
In all our tests we ran internally and for beta testers as well performance is somewhere between 10% to 100% faster depending on what you are doing.
It is always possible that some use cases are slower. We are eager to fix them if we can reproduce them.
For us to fix them you have to file a bug with the full 3.4.2 based project folder attached in a state where it can be opened on both 3.4.2 and 3.5. So that we can do comparisons and then optimize.
So far we haven't yet gotten an actual project folder from this thread, that lets us profile and optimize. This is unfortunate.