Finally got a chance to play with mine over the weekend. I was a bit concerned at first because I couldn't get the OS to load, but I discovered that an older or knock off SD card may have issues with the device.
I was using a 16MB (yes MB, that's not a misspelling) SD card and it wouldn't pick that up. I switched to a newer 8GB microSD and everything worked great. The bios switching for SegaCDs is the main reason I picked this up, and it performed pretty well for most games that I played with.