You can read my findings and summary in the following thread:viewtopic.php?f=18&t=110163
Specifically, the uPD720202 (54mm 2-port adapter with power plug) is one to be wary about. You can read about some of its problem and solutions here:viewtopic.php?f=43&t=97779&start=90
While the workarounds worked for me, it is a bit annoying to have to resort to them. Unfortunate, that is, since the card works great once you disable L0s. However for your X220 the ASMedia ASM1042-based adapter (which I also mention there) may be a good solution.
Finally, you can get USB3.0 and eSATA in one package, by using an adapter like this:http://www.ebay.com/itm/Hidden-USB-3-0- ... 540ca873ea
I have one, it is also based on ASM1042, so I would expect no strange issues. It performs well, but seems to drain quite a lot of power, even when idle, which will affect your battery life. I haven't performed accurate measurements, but plan to at some point.