The menu refreshing problem is new to 10512 build. Hopefully, they fixed it in the new build.
That is the nature of development builds. There will be bugs. This is especially true for the fast ring. If you need your phone to be perfect, e.g. If it is your daily driver, it might be better to just wait for the official release.
Regarding IE, they had to remove it to make sure Edge is working and nothing is broken. IE was tightly integrated in the OS so removing it early is important to find the bugs and rehook some things to Edge. They did leave both for a couple of builds as I remember.