I installed 2112 on top of VS15 Preview 5 - the installer showed a checkbox for VS Preview 4. I went for it to see what would happen, and it killed VS15. The first VS15 startup after installing 2112 showed an error dialog saying to look at ActivityLog.xml. I clicked don't show this error again, then clicking the file menu made it exit immediately. Subsequent attempts to start VS15 shows the splash for a second and then exits immediately.
I figured yall would want to know this so the installer can exclude Preview 5 until support is added. A note on the website might be good too.
I'm also curios if there is a VA uninstall process that would restore the Preview 5 install without performing a full reinstall. I've done the reinstall of VS15-P5 followed by another VA2112 install - so I'm currently in a bad state (I wanted an accurate write-up for this post with a workaround). Let me know if I can attach any log files while I'm in this state.
So if there is a VA uninstall process I'm ready to test it out :)
Sorry about that -- we are working on an update for Preview 5.
In the meantime, you can get the installation working again by deleting the file privateregistry.bin located in this directory: C:\Users\<username>\AppData\Local\Microsoft\VisualStudio\15.0_<hash>
VS15 will start up as if it is a brand new installation. VA may or may not be enabled. If it is enabled, I recommended disabling it (Tools | Extensions and Updates).
Also note that many extensions on the VS Gallery result in the same dead after a restart or two behavior. And using Uninstall in Tools | Extensions and Updates may result in similar dead at startup. All of these states are resolved by deleting privateregistry.bin.