I've got an iMac. Switch was basically painless, only takes a few hours to get used to the entirely different interface and you're good.
iPhoto is a huge plus, much superior to other picture programs [good for organizing albums i.e pharmacy events]
No mess of cords in the back... everythings in the monitor. No spyware/viruses/popups, no disk defrag, no computer randomly grinding to a halt...
iTunes runs much more flawlessly on a mac, and quicker.
So incredibly convienent to have everything in a monitor... this "desktop" is so mobile. I could unplug everything, move it into another room and have everything hooked up [including sound system] in probably 2 minutes.
My PC had about 15 cables running around in the back of it, from the sound system, monitor, printer, mouse, keyboard, internet, monitor power, printer power, etc. It was gross, took forever to unplug ****.
Downsides: Not a huge fan of quicktime.
If you're going to use a computer for browsing the internet, listening to the internet, watching movies/media, and typing up some papers MACs are ideal.
If you're a hardcore gamer, i'd recommend a PC. That's about it.