So 1 of my key targets with my new (relatively) n900 is to get rid of the vulnerable FAT from it. So far I've managed to format my Kingston 16GB class 10 microSD with ext3 and it runs most beautifully (instructions can be found in maemo website). Next step is repartitioning and charge filesystem of internal memory (the eMMC) to something more resilient like the ext3 or nilfs2.