I use Sandisk Ultra II 2gb cards and Transcend 150x 4gb cards. The latter are, as far as I know, the only non-SDHC 4Gb cards.
They all work fine. I use 2 Nexto units to store images. Quite inexpensive; add your own drives in whatever size you need, and with the extra battery you can download 100Gb per charge _very_ quickly. With the external battery it's still smaller than the Epson. I sold my Epson P2000.
Leica M's, Mamiya 6 's and many off topic items