I am doing further research into which instances this modified kernel is safe. There are two: one that increases read speed - in which my understanding is that it will work with newer cards based on the MMC4.1 standard (not the included 64MB card), and another one that adds to the first hack, but also increases write speed via multiblock writing. This multiblock kernel is what I am using now and it has dramatically increased the speed of my Nokia. However, I have only tested the multiblock kernel with a Kingston 2GB MMCMobile card.