Here is my opinion:
Windows:
Positive:
- Good for games
- Compatibility with major software;
Negative:
- Price
- Often slow
- NTFS just sucks
- It's bootloader only detects Windows systems
- bloated.
- The Windows updater only updates Microsoft-software
- Every new Windows version needs more and more RAM.
Mac OS X:
Positive:
- The design?
Negative:
- The price (Macbooks cost $3000 or something)
- Extra hardware needed
- I heard that even Linux got more software
Linux:
Positive:
- You can do what ever you want with it
- Much easier and cleaner software-management than under Windows (updates whole system by one command)
- Most advanced kernel ever
- ext4 > NTFS
- Most of the supercomputers use it.
- Programming is much easier
- Excellent for Hardware from Stoneage
- Compiz kicks Aero's ass
Negative:
- Needs time to fully maintain
- Not so much games