If you're happy with what you've got, why switch?
I've been using Windows since it was a shell and not an OS, Linux shortly after, and mac was added to my collection just a few years ago.
I think all operating systems are fine pieces of software, though all have their advantages and disadvantages. I'm not going to say much about linux, because that's not an OS in question.
Windows is great all-round, but is much more susceptible to malware. I found running without admin privileges virtually eliminates all threats, without installation of additional security software. Though this works only as well as the user is smart; it's still a good idea to have some protection.
Mac desktop is great if hardware isn't a big deal to you. The hardware is acceptable, but not the best in my opinion. Though, if you want 'the best hardware', you'll be buying new equipment every few months wether or not you go with mac, anyway. Mac desktops (Excluding mac pro) are difficult to work with, because the cases are so proprietary and confined. None of the components are field replaceable. (iMac has panel on bottom of computer for RAM) The Optical and HDD requires you to open the case, which is probably as easy as open-surgery heart transplant. Other components such as GPU are soldered into the main board. Most mac desktops have no expansion, except through USB or blue tooth. Mac Pro is more like a PC desktop, but without standard PCI ports; it has PCI-e in its place.
For laptops, I find the hardware quite acceptable. Just a little pricey. Though mac laptops are considerably thinner than most PC laptops with similar specs. Mac laptops have the same general disadvantages as PC laptops, as far as hardware. Such as the graphics chip being soldered to the main board, minimal expansion/upgrade options, etc.
As far as the OS goes, I like it over windows because the UI is great, especially for laptops. You should check-out some of the features of Exposé. Second thing I like about the Mac over windows is that Apple doesn't treat its customers like criminals. Mac OS X doesn't have any serials, activation or even any kind genuine advantage program. Other than that I find both OS' equal.
Though if you're into gaming you may want to steer-clear of mac, not only because the graphics chip is likely to be soldered into whatever model you get, but because OS X has a small selection of games, and what games it does have are almost all shoddy ports that hardly run at all.
In the end we all need to realize that computers aren't gaming consoles or MySpace machines. They're just tools to automate tasks. All they do is receive data, store and/or manipulate it, and output it when/where needed. As long as the hardware and OS can do this, I really don't see what's wrong with that system or another.