We have a new beta for Start8 (v1.17) which includes various updates including fixes for some issues with the Windows 8.1 preview.
•Updated for Windows 8.1 preview build compatibility
•Start8 allows customizing the Start button image AND provides a desktop Start menu
•Added new prompt on first run to select a default button image. Upgrade installs will not see this prompt.
•When running on Windows 8.1 Preview, respect the OS configuration for "boot to desktop"
•When used with Stardock WindowBlinds, you can also override the Start button in use with the WB setting for "always use the OS" button
•Options for showing the Windows 8.1 Start screen in other than full-screen mode are disabled in this version of Start8