This is basically the scenario that I went through this last month. You can read about it in more detail here:
This is an overall frustrating problem. The fact that spent a bunch of time trying to impletment an eSATA connection to my computer only to find that the USB 2.0 driver is faster really irks my chain.
I guess I'll stick with USB 2.0, although it's really disappointing that SeaGate even put an eSATA output on the FreeAgent Pro if it was going to be that slow. I'd have been happier with FIREWIRE 800.