FWIW, I connected the same external drive used in my eSATA test but this time over USB 2.0 (it's a cool enclosure -- takes both PATA and SATA drives, has USB and eSATA ports). The results were:
Linear Read: 29.7865 MB/s
Random Read: 3.1554 MB/s
Access Time: 8.25ms
Overall Score: 3731.
Not bad. I would have expected more bandwidth to have been wasted with control signalling.
RonS, do you know whether drives mounted in the UltrabaySlim port on the ThinkPad itself suffer the same 34MBps limit? Since the UltraBaySlim can take a PATA HDD over the same connector that the SATA caddy uses (with no translation hardware), I wonder if the port is PATA (would make sense given that it's usually used for optical drives) and the SATA caddy adapts the drive to the PATA bus.
This would explain why the choice of SATA drives usable in the UltraBay Slim adapter is limited like it was in the T43 which used bus translation on the primary drive.
Further, if UltraBay Slim devices are all exclusively PATA, the dock would have to support the same bus and would also have this limitation.
rbsrao79, getting back to your original question, that would make a PCIe eSATA card your best choice (I'm assuming here that the dock doesn't have room for an internal hard drive -- does it?).
One caveat. I just installed a PCI SATA/eSATA card in a legacy machine. The SII card that I installed said that it supported RAID, but I ignored this because I didn't need RAID. What I discovered is that one HAD to use RAID with this card, even if it was an array of one drive. This was unusable to me as it would make the drive unmountable on a non-RAID controller.
Fortunately, the BIOS was flashable and I found the BIOS used on the non-RAID variant of that card. After flashing the card I was able to use it without RAID getting in the way. I wonder if I could have saved a few bucks by ordering it without RAID in the first place.