Apple will cull their hardware line a bit further with the release of Leopard in October. According to AppleInsider, the latest developer build describes the system requirements as "...an Intel processor or a PowerPC G4 (867 MHz or faster) or G5 processor." My own 1.25GHz iMac barely makes the cut, which means it will run Leopard slowly, even packed with RAM. Other machines, like the 800MHz PowerBook G4, Quicksilver PowerMac, iMac and iBook, aren't so lucky.
And with that, many of us suddenly have "vintage" machines. I remember finally replacing my 333MHz iBook when it refused an install of iMovie, due to screen resolution requirements. Perhaps this experience will finally get the old iMac off my desk.