I wonder how many of those who "NEED" Windows are comparing a modern PC with a 10 year old RISC OS design?
The fact is an Iyonix can do a lot of things out of the box that an RPC either can't do at all, or can't do without hardware add-ons and even then will do it less quickly than Iyonix.
I have an Iyonix at home and find that I don't need Windows at all. OK. I use Windows at work and am using it now, but that is because it is the computer my employer has put on my desk. I am not aware of anything I do with it that I could not do equally well with the Iyonix (except perhaps logging in in the morning and accessing a few badly designed websites).
If your RISC OS machine is an RPC or older, you may find that it cannot do some of the things that would be possible with a more modern machine. But that more modern machine could probably be an Iyonix, it doesn't necessarily have to be a PC.