Dougal: Stagnation only occours when a platform manages to do exactly what the userbase wants, and they see no need to upgrade.
Look what happened to the RiscPC. Fantastic platform with damn good software, so no-one bothered(or needed!) to upgrade for donkeys years. Effect: greatly smaller cashflow through the companies developing the hardware.
Now look at the PC. Doesn't do what the user wants, fools upgrading this that and the other part on it every few months - Effect: one hell of a lot more cash being thrown at hardware/software