When your fingers are too fat and/or your hands are too big for a Libretto, or you have pathological issues troubling the relevant appendages, then do yourself a favor and don't bother.

It's obvious: These keyboards are, or should be, primarily made for mobile people, so high quality and tray or coffee table compatibility are a must. The Psion 5-series keyboards are ideal for this as long as you don't fuck with the formula.