I was really scared about upgrading this when I saw the reviews about stability. But for whatever reason, I went for it anyway. Ive got a pretty hefty project coming up so I spent this weekend doing simple tasks to learn the ropes. Occassionally, key commands stop working and it seems like it really bogs down. I was used to seeing real time render but when an effect I created was really slow, I thought I had done something wrong, only to discover it was actually chugging out frame by slow frame. Id have to save and quite and re-open several times during the day to kill whatever was bogging it down. Im also a little disappointed in the library. Okay for $49 what was I expecting. I guess my disappointment REALLY stems from not being able to import older libraries from previous versions of FCS. Maybe theres a way to do it, but click-and-drag sure didnt work. I just need some more time to see if theres a way to import all the older libraries. Edit: Reducing my rating to two stars. I worked on my first major project in Motion and would have to shut down the program every 30 minutes. Thats not counting the beach balls Id get about every 10-15 minutes, some of which required a Force Quit and loss of work. It got to where I hit cmd-S after every single edit. This easily added hours to my day that I really didnt have. I sent every single crash report to Apple. This stability issue really needs to be fixed. I dont understand why FCP X has "autosaving" but Motion doesnt. I didnt realize this until I lost about 2 hours of work on the first crash. I was so upset I could have thrown my Mac across the room and shot it. Edit for 5.0.3: As my new title says, Im cautiously optimistic this version fixed the crashing and beach balling bugs. I worked on a small project and did not have any issues on the scale of the prior version. Edit 6/8/13: I have no explanation for what has happened, but Motion will simply not stay open any more. If I try to create a new project, it beach balls on that startup screen crashes. If Im lucky enough to get into an existing project, within 5 minutes of clicking things in the library, it beach balls and crashes. Ive sent every crash report. I have completely uninstalled the app and removed all traces of it with an uninstaller app. Three times. Ive run the repair permissions. Ive got all the major OS updates. This app is dead to me.