After having spend some time with Motion to fully test drive it I have to make some comments.
First of all its a lovely Apple Pro App interface, nice clean and seemingly fast (at first). Like all Apple application that I ever tested its a typical 1.0 release: means its still a late beta and should have been proclaimed as a public beta as such. It crashes left and right its very far from stable (testing on a dual 2 ghz first generation G5 with 1.5 GB Ram and two serial ATA hd and the latest greatest OSX 10.3.5) great features you are getting final cut that would make crashing less painfull are missing (auto save, auto recovery etc.). So much for the first impression. Getting into it is EXTREMLY easy if you ever used Final Cut and even easier when you are an After Effects pro. Things are where you expect them, if they are there. And with simple comps its the fastest motha of all out there to do compositing. I would even go as far as to say with the right kind of footage its realtime. Until you add 4th layer with effect - then the program is not realtime anymore and to my surprise does not allow me to have some kind of prerender (ram preview for the AE diehards) how in hell would I judge the timing if its all jumping over frames sometimes jumping from first to last frame in the timeline. maybe I missed this feature if not without it its almost impossible and reminds me of After Effects 3.1 with RAM preview where you had to render your files. Except that the rendering does run FAST with motion even if not realtime for more complex compositions its fast. Stop the preview before you render because for some odd reason it tries a realtime preview in the background while exporting in the foreground with no way to stop the realtime preview while exporting making the export(render) take 3 times as long.
Well this is about it. Yes I told you about the whole programm. Where does this leave us. With a very neat little application and when I say neat and litte I mean it. Its a good addition to a toolbox but its very far from replacing AfterEffects. It lacks multi composition treatment in one project. It even lacks any time manipulation of the clips (no you can not freeze frame a clip without going to an external programm!) The plugins are kinda sparse and it feels pretty uncompleted all over the place. The good thing is that if Apple decides to update it often it has much potential upward so I would wait until 3.0 to put it into a professional production pipeline without room for experimentation.
PS: I kinda see a VJ application in there everytime I got the chance to play with it. The realtime manipulation of fxs is way smoother then anything else on the market (until it gets kinda complex that is)