I am a windows and osx user. I use windows on my main machine but love OSX on my laptop. I find OSX to be much better designed for laptops that windows (IMHO).
1. The battery life on Mac laptops is great for the price. You have to go to the upper echelons of PC laptops to get the same battery life or better.
OSX is also very good at managing battery life, better than XP and Vista.
2. They are designed brilliantly, and i don't mean "OMG it's aluminium", with nice smooth edges which make them easy to hold and comfortable on your lap. There are no sharp edges to digg [sic] into your legs (MB palm rest excluded).
They also feel great to hold and use
3. They come with great hardware as standard. I love having Firewire, built in camera, built in remote sensor and remote (for music or video with an external screen). If you go Pro then you get a brilliant back lit keyboard and ambient light sensor.
4. Great keyboard and excellent big trackpad makes working on them a breeze compared to similar windows based laptops with small track pads and cheap keyboards. I know you can buy a lot of laptops these days with good keyboards however very few come with a nice sized trackpad. You'll find other laptops trackpads very constraining after using a MB or MBP.
5. OSX is a very good operating system. It takes a while to get used to the differences but there are some things you will really miss when you go back to windows, such as:
a. Exposé
b. Drag and drop everywhere
c. Spring loaded folders
d. Spotlight (which is a lot faster than the search in Vista)
etc.
I could keep going but hopefully those are some (slightly biased) reasons why mac laptops are worth it.
The thing that made me switch in the first place was really iTunes and the way CDs could be imported and burned while windows only had the very restricted Windows Media Player, able to play .wav but not convert to other formats or burn CDs. And although iTunes is now available for free on Windows, it really speaks volumes about the Mac experience - it is all about programs being able to offer you as much flexibility as possible without continually having to buy extra software or download more and more. For example, you can create .zip files direct from the Finder without WinZip or Stuff-It.
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Other plus points are that OS upgrades are cheaper than MS, and so the list goes on and on. Add to this how many committed open source and shareware programmers out there that will help you out when MS provides obstacles to compatibility and using a Mac will give you the feeling of being part of a straight talking community that will willingly give assistance in the many forums that exist.
Some of your points are good and valid but some aren't.
Windows media player has been capable of encoding MP3's and burning CD's for a very long time. Also windows itself has a lot of excellent third party music player software which leaves Windows media player and iTunes in the dust.
Also you can easily create and open zip files in windows without extra software from at least ME/2000 on.
Apple upgrades are cheaper per upgrade but come out far more often than windows upgrades so this is not really a valid point.
Also Apple provides obstacles to other companies with their own special file types and storage. This isn't a windows only problem although they have been called out on this in the past.