Anvil - this is important:

http://www.ocztechnology.com/ssd_too..._Edition_SSDs/

There appears to be only one Firmware on the OCZ website, called V. 1.05
Yet you state on page 1 that you testet with FW 1.0 - can you confirm these are different FW revisions?
I fear they may have imposed the slow 4k performance onto the Vertex LE as well.. or at least onto the 50GB model.