This is an important milestone! Not only is this the first beta build for Unity 5.5, but the first Linux editor build shipped from a unified codebase with mainline Unity. That may not sound exciting, but it has a lot of exciting implications. It means that, instead of starting with vanilla Unity and piling thousands of custom changes on top, all of our changes now live in the Unity mainline, where they can be constantly punished by our automated test suites across all of our platforms, and where all of our developers across Unity can easily fix, refactor, and extend Linux editor code alongside everything else. (As an example, the window dragging fix mentioned below was contributed by @shawn .) This also means that your bug reports will be easier to track and test, and the fixes easier to verify. In addition, your bug reports will now go directly to the main issue tracker instead of being redirected here to the forum. You're still welcome to post here, and we'll still be reading and responding to your posts - but when you encounter a problem in Unity, Help->Report a Bug will now give you the standard reporting tool for describing the problem and uploading your repro case to us.