markee174: "Has Windows/Linux/Mac or anything really changed? Still built around essentially 1970s technology..."
Actually, Windows has changed quite a bit over the past decade. Windows XP, 2000, NT all have technological heritage from grown-up operating systems, whereas Windows 98, 95 and earlier were based on DOS. Mac OS X is based on a microkernel and BSD UNIX, whereas Mac OS 9 and earlier were microcomputer operating systems dating back to the early 1980s. Linux has been a proper multitasking kernel from the start, but observe the increasing attention and capabilities of GNU/Linux from its conception up to the present day.
Sure, recent versions of all the mentioned operating systems reuse a lot of work from the 1970s and earlier, but just because we're living in the 21st century doesn't mean that it isn't relevant work. What happened in the 1980s is that microcomputer designers had to make some major compromises and this affected the capabilities of operating systems available for them. For a good ten years, we've seen computers that have outgrown such restrictions, and the compromises aren't as relevant today.
Windows and Mac OS have changed to adapt; RISC OS never did. This lack of adaptation is a crucial reason why RISC OS isn't regarded as a primary platform for most users and developers these days.