All I can tell you is that there could be some problems with third-party plugs. Logic 8.02 is not more stable than L9. I am one of the lucky users who can work with the Gold Master Build of Snow Leopard 10a432 over the developer base and I would never go back to L8. I have no more memory problems and now Logic goes so fast I never thought it could happen, so I am very sure that some of your problems will be solved after changing to Snow Leopard in September. Now Vienna must release (VERY VERY IMPORTANT) the 64bit versions of VI and VE, then it should work perfectly. Logic 9 is optimized for working on Intel-Macs. If you are user of PPC-Mac you can work with L9 generally, but for working optimally you should stay with OSX.5.8 and Logic 8.0.2... but be sure that L9 is not the main reason why you would have problems with your stability, so please check all your plugs for compatibility. The memory access could be a problem....
Best,
Nico.