First, mapping rig point to a model still requires manual rigging. In other words, there is still no automatic rigging in Unity 5. It is 2015. Automatic rigging on simple models should have been possible by now. Furthermore, Github user ***** already made his automatic rigging algorithm open-sourced for programmers. Surely unity could easily integrate the algorithm into Unity engine.
Second of all, the Unity Store feels and works outdated. When downloading a tool or a scene from the store, you have to click multiple buttons and yet sometimes the download does not start. Furthermore, the download speed is abysmal. This is a problem to beginners who always need assets from the store for practice.
Third, plane tilting affects everything. Sometimes, you only want certain aspects to be affected when modifying or tilting a plane. However, Unity cannot handle it properly, resulting in errors or unwanted contrast difference or tilted light origin unexpectedly. This greatly affects high level users. One way to handle this situation is to use integrate everything into a single object during plane tilting. This may hog RAM, but it might be the best way to handle such simple menace.
Unity 5 is great overall, needs to fix some issues and it will be the best open-sourced engine out there.