As you know I run a Developer Beta of the Catalina OS. I just installed 10.15.3 Beta 3 on my Developer Beta SSD. It installed just fine. I am sure there are fixes within this update, but what interested me the most was the speed of launching Apps. I can say without hesitation that Apps launch very fast in this Beta update. Of course, I don’t have tons of Apps installed in the Beta, but all things being equal it still is quite fast. If you are doing a regular Beta or a Developer Beta go ahead and install it.