The txtr e-reader has a 6" display, and supports ePub files. It has a microSD slot (ships with a 8Gb card), and has USB, Wi-Fi and txtr Net wireless service (works in Germany only) - in which you pay 22$ a month.
It runs an ARM11 processor, and it will be an entirely open platform for developrs. Pre-orders start at December 1st for 477$. Via e-reader-info.