So, The G4 is a PPC 32bit CPU. The G5 is a PPC 64bit CPU. The Intel Core Duo is an x86 32bit CPU. The next intel chip is an x86 64bit CPU. Windows Vista will be a 64 bit x86 OS, with 32 bit compatibility mode. I'm very curious how OSX will work in the future... 32 bit / 64 bit modes, x86 / PPC modes... someone's going to get left out along the way. Personally, while I love these new Intel Macbooks, I'm going to wait until they implement Intel's newer CPU, which will be dual core, higher clock speeds, lower power usage, and 64 bit. So obviously, if you want to be the most future proof, you'll want an x86 CPU which is 64bit. The Core Duo that is in these macbooks is codenamed Yonah (32bit). The successor to this chip, codenamed Merom, will be out later this year. I'm sure everyone knows about the whole x86/ppc/32bit/64bit conondrum out there, but I thought i'd be redundant and make sure everyone knows .