I've had my N800 for about a month, using Kingston 2GB SD in internal slot (/, swap), and PNY 8GB SDHC (maps, movies, dictionaries). I've transferred movies and dictionaries via USB (Mac OS X), and maps via download. The only anomaly I've noticed is the difficulty in unmounting the cards from the Mac. After USB transfer, the N800 has to be restarted in order to show the internal card.
V Mabus