I haven't been too impressed with the higher numbers so far, but probably more because of the OS rather than the hardware...
ATA66 controller, ATA100 drive, 733 Celeron, FreeBSD: 60-65Mbytes/sec
ATA100 controller, ATA100 drive, 1.2GHz duron, Win98: 28-30Mbytes/sec
Not really a surprise that FreeBSD excels even with lower end hardware.
Windows can't even use a third of its burst capacity while FreeBSD is nipping at the maximum...