My Cisco 350 card (with additional drivers) and my Toshiba 5Gb PCMCIA drive works.
Both can work at 3.3v (I use the Cisco for reception mainly as it has an antenna socket)
I also have some specialty SRAM cards, and other memory cards seem to work.
Battery drain is heavy, but not much more than some similar CF cards (microdrive and WiFi cards other than socket).