I've just installed a SanDisk prerelease 6GB CF card as a replacement for the internal microdrive in my SL-C3100.
I do have to admit, having a high speed CF card really does make a difference. So now I have the following configuration:
Internal CF card 6Gb (three partitions, EXT3, EXT3, FAT32 similar to the original config)
External SD card 1Gb (Just for music and such, FAT32 filesystem)
External CF 802.11b card for networking
I'll need to post a picture-by-picture takeapart of the process, since dissasembling the 3100 is a bit tricky, and it's knowledge worth sharing.
Beauty in motion.