Depends partly on what you're doing at home. I do photography stuff in Lightroom, and it needs a pretty fast processor and plenty of RAM. The large, crisp monitor is a big plus. I have a couple little databases and a handful of simple spreadsheets at home -- I make do with Open Office. But you're right -- for the folks that surf and use e-mail, or students that just need a word processor, spreadsheet and presentation package, about any hardware will do.
One other point about Mac -- for years I've wanted a single calendar/contacts solution. Ever since I moved off paper. I'm talking back in the Palm Pilot days, up through the early smartphones, Yahoo/Google web solutions, etc. Only since I got Apple stuff has all that synced perfectly without any effort from me. The core is Exchange here at work, with iMac, iPhone, iPad, and Macbook all working in perfect harmony. I'd like to buy the world a Coke.
We're on Win 7 here at the ol' saltmine. No real complaints. No word when we'll migrate to 8, but it's never fun.