Macs run the Mac OS, not Windows (unless you go to some trouble-more later), so you will probably need the Mac version of your desired apps. But there are a ton of Mac apps and they are far more uniform and (typically) reliable than Windows applications are.
Monitor-maybe, but you might decide you want better than what you have (this is true of any current-day new computer purchase)
Mouse-probably. If it's USB, absolutely!
Printer-probably, but the particular printer you have is important.
Macs aren't that much more expensive than comparable PCs, and they are "integrated" much better than most PCs. In other words, you won't have crashes because of hardware conflicts, such as if Dell decided to use this particular nVidia card but didn't bother to get the full retail version and all your programs expected the stuff on the full version. It IS worth switching for the ease of use and consistency of performance.
People use Windows XP and Vista on their Macs because 1) they can and 2) there are some programs that have no Mac equivalent and they must run them. All new Macs are built with the current generation of Intel processors (almost all of them Core 2 Duo processors), so it's possible to natively boot into Windows if you like. It's a great way to see the effect of different OS designs too. Yes, MacOS IS superior in many ways.
Office? There is a Mac version and it works great-I use it myself. Front Page? It's poo, pure and simple; Microsoft gave you a program that writes horrible and bloated HTML code. There are a lot of WYSIWYG HTML editors available for the Mac, and they're all not only better than Front Page, they write STANDARD HTML code, not the gunk that Front Page produces.
Your existing games will work only if you boot into Windows, but as I mentioned, you can do that if you want. Gaming is one of the few things that makes putting Windows on a Mac make sense to most Mac users.
As for bias, I have been a PC owner and user since 1985. I got my computer science degree using PCs and PC-oriented development tools. Macs are indeed better for most people.