Ok, so to the popular belief that Apple maximizes full system efficiency by matching and optimizing hardware to software - this tells me that any Mac is at its best at time of purchase with its native Mac OS X version (because the software was designed to take full advantage of that particular hardware). If that's true, then does upgrading the OS, say from Snow Leopard to Lion, reduce that efficiency? Because Lion will be tailered to the next generation of hardware...? Or is the level of efficiency the same, so long as the hardware meets the min specs of the OS? As you can see, I'm already debating on the upgrade to Lion later this year, and its impact on my 2010 Snow Leopard MBP..