My final thought before this gets too off-topic:
My dad uses an old iBook G4 for most of his daily computer activities (word processing, browsing, blogging, email, Spotify etc.) and he would probably wouldn't benefit much more from a more recent machine. In fact, he's got an Intel Mac Mini that gets nowhere near as much use as the iBook (although at least my mum can actually get a look-in on there). The only real difference in his mind is that one's a laptop, the other isn't.
Additionally, I always keep in mind that a computer's just as fast as it was when you bought it. If your needs haven't changed then it'll probably still do the job just fine. I bought an iMac G5 just a couple of months Apple switched to Intel and only upgraded 3 years later when I needed a notebook for portability. I know there are different cases for different applications and uses but my point is that if something does what you need then there's no need to upgrade. That's not to say it's a bad thing to upgrade though.
Enough. If you've got an compatible Mac, if you don't mind Steam and if you want to play an awesome game then go and download Portal before tomorrow.
