I have just added a 32GB class 10 microSDHC. I put large vfat, 768MB swap and 5GB ext4 partitions on it. I'm using the swap space at the same priority as the internal swap partition and this seems to help quite a bit when doing things like simultaneously running mappero, the media player and microb. The ext4 partition is dedicated to easy debian, again a nice improvement over the loop device file.