Reports I have seen say it will run faster on 9.2.2 than on X, but that X performance gets faster with each revision. Most people are disappointed with this game's performance on Mac compared to a PC, myself included. It will still run though, and is a fantastic game even if you have to run at low detail. You'll see some posts by me in here:
G4/450 (first release fo Sawtooth models) with a GeForce 2MX ran fine. Detail levels were dropped a bit to accomodate and I found some levels really bogged down with more than 2 dozen critters on the screen at once...
The only problem I have found is difficulty micro-managing in large online battles when detail is set to medium or high.
If that's not a problem for you, you should be able to run at max details all the time.