I have a new Retina MBP which came with Mavericks. I have some issues starting Avenue... sometimes the splash-screen shows then nothing happens. The app never opens, and I can't quit the stuck process. The strangest part is that even a Force Quit does not work. The process still shows (as unresponsive) in Activity Monitor. The only way to recover from this state is a full restart (which also takes an unusually long time, I'm guessing because the system is having trouble shutting down the process).
So far this scenario has happened around 5 times, I don't know how to reproduce it consistently.