In an interesting move, the folks over at TaiG have released a new version of their iOS 8.4 jailbreak tool for Windows, but have labeled it as a beta. Version 2.3.1 beta incorporates the latest version of Cydia, version 1.1.20, and that's about all.
According to the change log, no other changes were implemented into the TaiG tool outside of the Cydia update. For such a small change, it's weird that they've labeled it as being a beta, but maybe this will become a new trend going forward until they have enough successful testers to deem it a stable release.