I too don't really like the fact that the CPU is not upgradeable in the Iyonix, but it'll only be an issue if and when Castle make a faster Iyonix. If they do motherboard swapouts for a reasonable price, that's fine by me.
However, and it's a really big HOWEVER, the Omega's fancy FPGA features (FFF) are vapourware ATM, and as has been pointed out, the StrongARM and 133Mhz RAM are both out of place in a brand new desktop computer.
I'd love to see the Omega perform in all it's glory, with all the announced features, but not only are they not available, we don't even have a timeline for when they will be.
As for running discontinued 26 bit software, unless totally unavoidable, IMHO we should be trying to use the actively developed software and fund the active developers rather than use software which has been cast aside in favour of PC and Mac versions.
But again, I'd love to see some competition in the market and for RISC OS machines to break the magic 1Ghz barrier.