A simple dd won't saturate the drive, though it might have a decent shot if drive "read-ahead" is enabled.

Things for you to do:

1) upgrade to OCZ firmware 1.3 immediately, if not already on the unit.

2) ensure the drive is set for highest performance:
hdparm -W1 -A1 /dev/sdx

3) stop benchmarking, and just enjoy the speed!

As for AHCI, its pluses are (1) it's now a multi-vendor standard, which means new devices that implement it won't need to write drivers from scratch, and (2) it fully supports NCQ (multiple overlapping R/W commands at once to the drive). Point (2) helps servers much more than desktops/notebooks, and benchmarks generally show that the OCZ Vertex doesn't really take much advantage of it.

Cheers

Cheers