Just to clarify some points about my article: I don't suggest for a second that RISC OS has a suitable UI for PDAs, and the devices which I suggested all have decent sized screens, probably better resolution than you'd run a RiscPC without VRAM, or an A7000.
Druck makes a very valid point about the lack of a vibrant software market, he's of course correct, but I think it's easier to make a vibrant market on these kinds of devices than on the desktop, simply because it's much easier to write the kind of app people run on ultra-portables (email,calendar,simple word processor, IM) than the type of app people run on desktops (Big Office packages, advanced drawing, photoshop).
The basic sentiment of the article is that I'd never buy a RISC OS desktop, unless I had abundant amounts of money, purely for a "fun" machine. However, I'd certainly buy an Ultraportable RISC OS machine, because the kinds of things I do "on the road" are simple, RISC OS is very, very up to the job, and an ARM portable would provide tangible benefits over dragging my MacBook around, such as weight, battery life, durability (no moving parts means fewer breaking parts), and the fact that some of these ARM devices are less than £400, my MacBook was £1100, so I'm wary about taking it with me sometimes.
It's not a cure-all solution, not by any means, but I think it raises RISC OS's chances of survival a little above zero, so it's worth considering at least.