Another didn't-do-my-homework mistake: Beware of buying one of the waterproofed models if you want to hack/mod your Kobo. On un-waterproofed models, the case is easily opened, and the main storage SD Card (IIRC - maybe it was a different kind of flash card) can be removed/replaced easily. On waterproof models, the SD Card is under the waterproofing layer, which would have to be cut through to remove the card.

My experience is over 2 years old, so I'm sure some details have changed.