I own a macbook, and use it for music, and would like to share some stuff with you.
I regularly use ableton live, but I have checked out Logic aswell. Wasn't really my thing. z3ta and massive both work fine without any problems. As does a bunch other stuff. I've a couple of different pieces of gear: 2 korg electribes, an access virus, two midi interfaces, a hercules rmx console soundcard, and a few other bits and shit. and a roland e-drumkit. The mac just slides in with hardware workflow really well. I've used PCs for years, and in comparison they are inflexible, clumsy, and you never really get free of configs and clicking on fiddly things. Granted, the mac does have a bit of this too, but overall the experience is way cleaner, refined and well worth the money to avoid having to experience how windows handles these same issues. The day to day experience with OSX is far nicer than windows.
I use linux full time at work (I develop digital TV software on an embedded linux platform) and am familiar how linux does things. Unlike the other 2, linux does not eventually get all messed up, it just runs and and runs and runs. It's also neat for development and data management, and has a well developed keyboard only interface. Drag and drop file management like you'd so in explorer is rubbish. I mention linux for two reasons, one to let you know I use a whole bunch of OSes and am not biased, and two, as OSX has, under the surface, a quite linux-like interface too. It's not quite as mature but its powerful and works good. When it comes down to it, linux is a powerful server/developer platform, and OSX is a powerful, comfortable media workstation. Windows is a gaming platform, techy, tweaky, unstable as hell and a jack-of-all-trades (and master of none).
Now the bad. My macbook has been working for 3 years, but the macbook hard drive died on me after just 1 year. I brought it back and got it replaced with a new one, but a year later that failed, but it was under guarantee still too, so I ended up with a new one again. They preinstalled leopard for me, which cost the same as the drive, so I came out mostly even. I often conenct and extra monitor and one day when i pulled it out the macbook crashed. It's had power problems ever since; standby mode never finishes and it just sits there with the fans on, and it takes 7mins to boot while it waits for some error to time out. These are big irritations but it works fine when its working. I suspect a reinstall will cure this. The reinstall is as easy as windows takes about as long. I wont even have to mess with as many drivers afterwards. BUT, since my OS came pre-installed on the drive, I don't have an install CD. I'll have to talk to the shop again, or download a cracked version. This is annoying and has been lingering for a while. I'd have solved it with windows by now by myself. OSX still outlasted a typical windows install before it started to get fouled.
The plastic on the edge of the keyboard has developed some crumbling. I think the build quality is not so good, but the modern machines use aluminium so it's probably better now.
So, in summary, while the system is up and running, it's lovely to use. Worth every penny, totally amazed me really. You cant experience the workflow it offers without owning your own. A few mins messing with it in a store is not enough, too bad. If you have the chance to get one, and are creative, like using computers to do things like making music and blogging it and downloading friends tracks, rather than tweaking and pimping your machine for the sake of the art for which it is, then I sooo recommend it to you. OSX is luxurious and expensive feeling and fucking NICE. Your problems with hardware and configs and updates and popups and antivirus and ads and bugs and exploits will all vanish. Poof. Lastly, consider the background and experience of people when evaluating their opinion. Some of the ppl here do not own a mac, and are dissing it. Personally I think this is because they haven't understood what using one for weeks and months actually feels like. And I've found it to be very very nice.
I'd be happy to answer any questions you have in private msgs. This thread will turn into a flame war and I'm not gonna bother reading it