It’s no secret that the first releases of OS X, starting with the Public Beta in 2000, were shaky. Your Mac suffered from subpar performance, even on the most powerful Power Macs of the time, missing features, and more crashes than you had the right to expect. After all, this was Unix, the industrial strength operating system, so why should you have to put up with so much grief?
Over time, Apple fleshed out the feature set, mostly. Some loyal users of the Classic Mac OS still felt neglected, but Apple chose to move on. Once hardware acceleration support came to the sophisticated interface elements, performance issues largely subsided. With the arrival of 10.4 Tiger, also the first OS X to run on Intel Macs, all seemed right with the world. By 2005, nearly nine years after acquiring NeXT and the services of Steve Jobs, the transition was an unqualified success.
With OS 10.6 Snow Leopard, released in 2009, Apple took a step back and cleaned most of the remaining rough edges. Some feel this was the most reliable OS X ever, but the reason most people use it nowadays — other than hardware limitations — is that it’s the last system to allow you to run PowerPC apps on an Intel Mac.