I found a bug in this bug fix.
When I start US2, either from Steam or from one of the two executables, Steam never launches it, and instead just ends up "Preparing to launch Universe Sandbox2..." until the end of time unless I stop it.
I'm pretty sure the game isn't yet awesome enough to require an infinite loading time, so I'm assuming this is a bug.
No this has never happened to me with an older version of US2 or any another game on Steam.
Yes I removed all local content via Steam and reinstalled it.