Thanks to everyone's responses, that's great. Although there seems to be a consensus that going from a normal-speed GS3 to a N9 would be like a drop in perceived performance... the N9 is just a slower phone? Overclocking wouldn't help me feel underwhelmed if I replaced my GS3 with it?

Thanks again for all these responses. Maybe I lurk in too many negatively-charged sub-communities on the Internet, but I have to say the Maemo forums have the most helpful people.