As far as transfers to and from a computer are concerned, just about any modern computer to CF adapter -- PCMCIA, USB2.0 or direct internal flash drive will blow away the the 1000s USB1.1 transfer rate, so that's too be expected.
As far as saving from the MPC to the flash card, it's hard to know how slow is too slow without knowing how much is being saved and how long it actually takes, but problems in this area (assuming they are not being caused by a broken flash drive or the infamous Akai corruption formating routine) usually have to do with either a slow/sketchy CF, or an excessively fragmented drive. If fragmentation is the problem, you should be able to solve it by backing up the files, reformatting the CF and writing the files back to CF.