If one really liked the hardware, BSD would be a better choice since most of the hard work has been done. However, the screen is really not optimal for X. It made a better character mode box for remote admin work.
I think that most people found that the StrongARM & MIPs were too much work for too little function.
Also, not much of a market. Sharp pulled Zaurus & Toshiba pulled Libretto. Current devices, many of which are not imported to the US but can be bought "grey market." Linux PDAs
People who need tiny laptops use something like the Sony Vaio T boxes, which are compatible with Debian. Debian on Vaio
original here.