Well for the customization aspect of it, like I said, there are sooo many widgets and apps you can get for it. Seriously for whatever you need. And I don't buy that it gets slower as it ages because almost everyone that I know, that has one, still have their Macs and they were extremely quick. And they've had it for a while.
lol That's because they couldn't do anything to it. I used a Mac for like 10 years at school and some of the shit they had were just terrible after a few years.
And User customization and mods > widgets and iApplications