Palmtop Nirvana?

cakefool asks: "There seems to be a Slashdot article every day about a new palmtop/subnotebook/digitalwhoojerammy, and without fail people complain it doesn't have what they want. Let's do this the other way around - what do you need in a handheld computing device, seriously? I ummed and ahhed for ages before finally ordering a Psion 5mx, and it does everything I need it to, other than play Doom(1), and is a hell of a lot cheaper than the JVC micronotebook, and smaller than a budget laptop, with a much longer battery life than both." What features do you look for in a handheld/palmtop computing device?