1) /tmp should probably be mounted as tmpfs, thus not touching flash at all.
2) Filesystems should probably be adjusted to line up with underling storage block sizes, have noatime and longer commit (or the equivalents).
3) Logging should be tuned, eg to reduce volume and frequency and syncing.
I noted some of the things I did at:http://www.earth.org.uk/note-on-SheevaPlug-setup.html#storage
PS. FWIW I have symlinked busy/large parts of /var/log and /usr out to my SD card.