I just received the Sonnet Echo ExpressCard/34 Thunderbolt Adapter that I order last week, as well as a third party eSATA card and tested it today with my external hard drive. My initial impressions are mixed. My first impression is that the box is much bigger than it looks in the pictures. It's about 4" x 3" x 1.5". Particularly next to my 11" MacBook Air, it looks huge, and with the 6' cord (unfortunately not included) it is a fairly kludgy way to add expandability to the MacBook Air (or 13" or 15" Pro that lacks an ExpressCard/34 slot). It shipped in one of those difficult to open plastic packages. It doesn't make for a great early impression. Given the size, it would be nice if it supported daisy chaining, but since it has only a single Thunderbolt port, this will need to be at the end of the chain (or your only Thunderbolt device. The list of "officially" supported cards is pretty small for now. Apparently certain cards need new drivers to work properly with Thunderbolt. My ExpressCard/34 eSATA card wasn't on the "official" list, but the driver installed, and it worked with the adapter. Once I got it set up, the ExpressCard eSATA port worked well, and I got similar speeds reading and writing to my external SSD (in the 120MB/S read, 75MB/S write range) in OS X on my Mac and Windows on my work PC. I attribute the speed to the cheap eSATA controller that I'm using, since the drive itself is capable of much faster speeds. Overall, I'd give the adapter a B. At minimum, it should be about half as thick (or thinner), and should have a second Thunderbolt port to allow for daisy chaining. Nonetheless, it is easy to set up (just plug it into the Thunderbolt port), and it appears rugged and well-built.