Just got the drive today, so I wanted to share my observations.
1. It works in XP & OS X, but it does so because it shows up as a USB device. I'm pretty sure that its usb in both windows and os x. I wonder of Lenovo only implemented the USB part of the express card spec?
2. It benches faster than a 8 gig usb stick I have, but not by much. It's about half as fast for writes as the stock 80 gb hd, but it's access time is less than 1 ms (compared to 17.4 ms for the hd). That may help somewhat with performance.
Anyway, its no speed demon, but it works in both operating systems and does not stick out too badly. I think I'm going to use it for backups.