I love Macs. My brother-in-law works at Apple and we gotta keep the family employed.

That said,
can you do this stuff with your Mac?
Translation: buy a computer for what it'll do for you. Yes, think about the costs of keeping it up. But, you gotta make the decision not just on that, but on what it actually does.
It's impossible to answer this question with a blanket answer. For some people the Mac is the right answer. For others, Windows is the right answer. For yet others, Linux is the right answer.
If I ran a store and was selling you a computer, I'd be asking a whole lot of questions.
1) Do you want to move around with your computer? (IE, do you wanna go hang out in the library or the Starbucks or the airport with your computer?)
2) Do you need it to do work with a corporate network? How often? What kind? (Need to know your email server, what kind of VPN, whether or not you have specialized apps that'll run only on Windows like Groove)
3) Are you looking for the best deal, or the best computer?
4) Do you use a video camcorder? Do you see yourself using that in the next three years?
5) Do you play video games? If so, what kind?
6) What do your friends use? Is there a geek in your life? What does he/she use?
7) Are you already familiar with a computer? Which one?
8) Do you have a home network? Are you expecting to own more than one computing device (keep in mind, that even things like Xboxs and Tivos are now networked computing devices).
9) Will you be looking to sync stuff with cell phones or PDAs? If so, which ones?
10) Do you read a lot on screen? RSS feeds, eBooks, or lots of email?)
11) Do you own a music device? If so, what kind, if not, do you see yourself potentially getting one?
12) Are you in the market for a personal video recorder? (er, a Tivo or a Windows Media Center)
Each question would help me take you down the sales process. This is exactly how I sold cameras. Your answers would cause more branches.
Keep in mind, not all of these questions would lead me to sell a Microsoft-based computer. I'm sure there's a few other questions that'd be good to ask too.
It might be fun to explore the right questions to ask first.