I installed the Mojave Beta 8 a few minutes ago. It seems to run really well. I tested the usual Apps that I use for my main workflow and all seems fine. Of course, depending on what Apps you are using, YMMV. I think the mid-September release of Mojave will go smoothly. Apple seems to be doing a lot of work on Mojave so that it works right out of the box. Hopefully this prediction will come true.
PS – OK, after working a little longer in the 8 Beta I discovered it does not like Path Finder, the Finder replacement App. That is disappointing, but many of these Apps that replace or enhance macOS System features usually do not release a compatible version until after the new OS is released. Will be hanging in there.