Julian>Yes a 64 bit chip even using a bit of a kludge of a command set like x86 is faster than an ARM. But you're not really comparing like-with-like here. The Windows OS is *very* much more top heavy than RISC OS and add to that the load of running AV software and the various services Windows tends to demand and you'll find the multi-GHZ clock doesn't quite yield the size of difference - and for certain things may even appear less responsive.
Yes you can cite FP being a bit down on the ARM/RISC OS and maybe disk write caching (a hazardous activity that appears to make the PC perform better) - but for running RISC OS programs a native platform is *still* best. As I said elsewhere Intel is beginning to encroach on ARM's territory - I can't see ARM simply retricting themselves to "microcontroller" level processors and letting Intel walk off with the richer pickings. And remember it isn't just ARM in this - their licensees have put IP into the ARM family - Intel (on the other hand) doesn't even allow second sourcing - so if Intel wins then Freescale/Texas/Sanyo/NEC et al will be the losers). So on the whole I'd be more optimistic about newer/faster ARM's coming along.