I recently sold my PRS-505 to save $$$ for a new 950. In anticipation of getting this unit, I also bought a 4GB SD card at a very good price from buy.com http://www.fatwallet.com/forums/hot-deals/1041461/
The Kingston HCSD card is rated as CLASS 6 - Minimum of 6 MB/s performance
Does anybody know if SD CARD read/write speed matters with this and other ereaders? thanks.