It depends what processor are you running..
I upgraded my p3 1gig board (512 of pc 133), from a geforce 2 ultra to a gforce 4 Ti 4600, and saw almost no improvement in Frame rate (tested with JK2). When playing music using winamp, and having it display the nice precreated video themes, I noticed that my processor would shoot up too 100% usage.. so I think as soon as I get my new Processor MB, and memory (going to a p4 with DDR 400) that I will see the FR improvement in JK2, and the processor usage on my system when running the winamp video, will be drasticly reduced... Basicly it comes down to the fact that the DDR memory on my TI 4600 is faster than my Processors FSB and I think it's bottlenecking there... but I could be wrong.