mripley: What software needs a specific RISC OS 5 version? All apps that have been made 32bit/ROS 5 compatible so far ALSO run on older machines (often all the way back to RISC OS 3.5, or even 3.1). Many Iyonix users report their machines are just as stable and reliable as their RPCs. In fact, Iyonix buyers that post in public forums seem a very satisfied bunch.
Things like USB are a bit foggier, though. Once a USB device is RISC OS compatible, it should be equally at home on a Simtec USB podule as an Iyonix.