Does 1MBps (give or take a few hundred KB) seem excessively slow ?
Based on what I'm getting with my ACA1230/28 (about 2.4M/s)and what the others have said, I'd think your 68040 should do better than 1M/s.
I'm using CF as well, but just the "standard" drivers that come with ClassicWB Full (I'm assuming that uses standard drivers, I haven't checked).
desiv