They're neat, not having moving parts, and being pretty damn robust, but damn are they slow to write to.
I'm sitting here waiting for 350 MB of files to copy to CompactFlash so I can bring it to work.
I've been thinking about making a directory synchronization tool based on CompactFlash/USB memory stick sneakernet. Have two hosts negotiate what files they have and their checksums, and each day going between home and work (or work and home), you put the media card(s) in and it gets the next 500 MB or whatever of the transfer. After a few days or a week you can move an entire directory, and faster than my shitty slow DSL upstream. And because both sides would keep/generate a database of checksums to locations, rearranging directories wouldn't be a slow operation to sync.
Okay, copy's done, I'm outta here.