hmm... this looks really interesting. I might be getting one of these as well, sense I already have $8.88 in DX store credit and could put that toward this.
I got mine. It is a GOAC with a separate board for SD card. The entire thing is smaller than a Dreamcast VMU mobo. Runs down to 3.3v, draws next to no power. No way to get Svideo or RGB I can see, but composite is good.
I swear it is true. See, it is like those N64 superpads: All the "guts" are near the center. The rest? Just traces going to button pads. The SD board is barely bigger than an SD card, and the GOAC parts are all right under it. Trim it to the caps on the controller lines, and bam, VMU sized.
Looking at some of the forums topics for that item, it seems that loading games larger than 4MB bricks it, and you need to reinstall the firmware to fix it.