I can think of several other things to do with a small (1M) RW fs.

For small files, it's faster to sync a Palm than an empeg. For things like directions, it's easy to put them in your Palm and it'd be nice to be able to send text files from the Palm to the empeg. This would also be handy for people who leave their empegs in their cars, but carry their Palms with them. I know this requires IrOBEX and without that available in Hijack, it doesn't seem like a likely use.

When the OBD-II gang gets farther along, it will be nice to write to log files for permanent storage. This data could be used to generate graphs for display on the empeg or via khttpd (mrtg style).

GPS data would also be nice to save to log files. You could use this to plot graphs of places you've been, distance travelled, etc.

I'd even find a history of when the empeg's been on in home/car mode interesting. From those logs, I'd be able to tell how much time I spend driving on an average day.

I'm sure there's other uses too. Between those things and wanting more graphics for khttpd to serve up, I'm thinking of popping a 2nd HD in there to store my own data on ext2 fs's.