hmm, dusky, not sure what has been done to screw up that indigo, but something's wrong if it doesn't work better and faster in os x than os 9. i may have 512 ram, but that shouldn't make that big of a difference.
in fact i was just in os 9 quite a bit after running disk warrior on one of my external drives that started acting up. while there i decided to play around a bit as i often wonder if i'm not just attracted to the eye candy of X. but frankly, it was slow and painful to do anything. file transfers between drives take incredibly long, browsing was ok, but not near as fast as icab in os x. program launching was sluggish, though i'll admit a few of them did run a wee bit smoother in os 9. but not enough so to make it a preferred os.
you sure that imac is fully up to date on it's systems - both X and 9? or perhaps there is one particular app or 2 that this applies to? because overall the experience in os x should still be far superior to that in 9!!