I was always a PC guy. My new job required me to become a Mac guy. Since working with a Mac, I have hardly used my PC at home.
As for web browsing, I use Firefox almost exclusively and occasionaly use Safari. I find the browsing to be at least as good as a PC.
I have a 23" monitor that I leave on all day, and use almost constantly. No problems, but they are expensive. You can always pick up a cheaper monitor if you use a Dell, etc.
The disads I know of are that they are expensive and that software can be harder to come by (depending what you are looking for).
Overall, the next computer I buy will be a Mac. More reliable, less hassle, and all so shiny.