Tablet supports MicroSD only. The keyboard takes full-size SD cards and has 2 USB ports. Harddrives and thumbdrives both work fine, but the really tiny thumbdrives don't fit because the ports are slightly recessed.
Yes it's a metal bevel and plastic back. The back is textured so it doesn't slide out of the hand easy, but on some of them their is noticeable flex between bezel and glass. Doesn't bother me on mine, but I have several friends who bought also and one is particularly bad.
Gotcha on the refurb, but I've always had good luck with them. (mostly Sansa mp3 players.)