It's hard to appreciate true multitasking unless you've exprienced it. But it's almost impossible to go back once you have (to either Windows 98 or OS 9). New users to a true multitasking enviornment I find have trouble taking advantage of it. They are sooooooo trained into waiting for the foreground task to finish what it's doing. In OS 9 if you have to wait a couple seconds for something, that's it you tend to wait those 2 seconds. In OS X, you take a glance at your InBox, read a little more of that PDF doc, glance at a web page. Those quick task switching episodes add up. And you just find you get much more done. Of course the wins REALLY ad up when you do some heavy lifting and feel the freedom to do something else at the same time rather than head for the water cooler.
Why OSX is better, reason 4: Can you say multi-tasking?