I only got a 2Ghz G5 iMac at the moment. (I am waiting for Leopard to go back to MacPro). My computer didn't handle the layers very well at all really. I had to improvise.
One technique that worked quite well was exporting all my Photoshop layers in 2 sets. High Res PNGs and 'REALLY' compressed PNG-8 for web. Animate them in After FX to get all the layers, animation and camera moves how you want them.
When you are done, simply reconnect the files in your project bin (the low res versions) to the high res versions. Make sure everything is the same by dragging through with your cursor at Quarter Res and then render all your shots over night.
Motion did handle a lot of this stuff better/quicker so I will try to create as much as possible in Motion from now on (using the same sort of techniques). Especially that it now has 3D layers/cameras.
After FX is still king though and rightly so. It's been on the market for a 'Long' time. It's got too many features that you find you need at some point. The 3D cameras/layers in After FX are better designed aswell... but that may be a case of me being used to the way AfterFX operates.
