I'm running Win7 on the low-spec'd 'home' computer that the rest of the family uses - 1.8ghz Sempron, 1GB ram - and it works surprisingly well.

I think it's got the best of Vista and XP and less of the garbage we hate. I think it will be successful if Microsoft can pull off a good marketing campaign. The difference between IT departments upgrading to Vista or upgrading to Windows 7 is that Win7 will actually run fairly well on their old hardware.