Most of the benefit of going to Mac is what you would consider "soft stuff" vs. hard savings. I would classify most of it under the heading of Productivity. It is little stuff, but lots of it.
Lets take an example. How many times have you encountered this problem? You are working on a file and you decide to save it to a new directory or a different disk altogether. No worries, right? Just use the trusty old "Save As" dialog and navigate your way to the new directory. BUT, that takes time, doesn't it? And that little Save As window can be tough to use for any extensive hunting for your destination. Now lets consider that same task the Mac OS X way. We start the same way, and the trusty old "Save As" dialog comes up. But instead of painfully navigating to my new destination folder (lets assume it is called "foobar"), I just click in the Spotlight entry area at the top of the dialog and start to type "foobar" - after just a few letters, Mac OS X has identified the "foobar" folder and taken the Save As dialog there. Job done! You just saved several minutes of pointing and clicking and scrolling... and lots of aggravation. This has to be my personal favorite features of Mac OS X.
Consider this sort of elegance spread over just about every feature you use daily and you have some idea of what a Mac can bring to you that a PC cannot.
Lets add to the list. Leapard is going to bring another big enhancement (IMHO), multiple desktops, called Spaces by Apple. If you have ever used unix or Linux, you will know that this productivity enhancer has been a staple for years. Multiple desktops help you control the clutter of multiple open windows. I use it for example to keep all my Web stuff in one desktop, all my email stuff in another, all my file management type work in another and so on. No more switching around trying to find a window you were working on before you got interrupted and had to check a web page... now where did my email client window go again? No more - just click back to your email space and there it is.
Like I said, small stuff, but LOTS of it. In two words, what a Mac will bring you that a PC won't is "enhanced productivity".
...and by the way, lets not forget the sleek good looks, the fact that Mac OS X boots in about 30s, the complete stability and freedom from the need for intrusive tools like Norton <just about anything they make> and so on.
