I don't see why anybody would get a Mac as their primary or sole computer. There's so much you can't do on one because Steve Jobs can't find a way to monetize it. I have a mac mini, which I only got because Jobs wont put out a windows or linux version of the iphone SDK. Thats the ONLY reason I even own a mac. And its a decent computer and OS but there are a ton of things that I do on my PC every day that I cant do on my mac at all.
Gaming...nope
Blu-Ray...nope
Transcoding videos (Nero Vision)...nope Titanium Toast 10 sucks compared to Nero
Flash videos without using 75% CPU...nope
Media serving...nope
Macs are elegant machines but they just arent worth the premium price when there's so many basic computer functions they just wont do.
Gaming... Ironic since Apple was accused of being a 'toy' computer in its history. There are games, many serious gamers are using consoles. The only place I see a desktop computer excelling is with MMORPs and the twitch shoot'em-ups.
Blue-Ray... Streaming HD or downloaded HD content for OSX. Blu-Ray would make sense in a Mini set up as a media center, sadly that is not available.
Transcoding... free option is Handbrake (unless I'm not clear what Nero Vision is doing), other options are available
Flash videos... Adobe is working on it and yes Apple may not be helping. Ideally we would not be using Flash just for video. Historically it filled its niche well, today its a resource hog on either Mac or Windows, moreso on Mac.
Media Serving: Try Plex (based on Microsoft Media Center), MediaCentral, FrontRow or Boxee. Perian is an extension that adds most commonly found codecs for Quicktime playback.
The biggest thing I hear from anyone claiming superiority of Mac or Windows is what each has as a strength. In reality both are capable as an OS, some features are easier on one over the other. In some cases it requires most cost or more time in setup. Software support may be broader when running Windows by more vendors, but the majority of applications and needs are definitely covered in OSX, when not virtualization or dual booting is an option.
Undeniably, viruses and malware are a greater issue when running Windows. Security may not be the only reason for why the Mac OSX is not affected more than windows, but in reality running the MacOS requires much less effort to maintain and protect the system from malware.
Advocating either platform choice or not, it is ultimately preference, cost, ease of use, software availability and experience that helps inform a user on what system is right for them.