1.) Why do you like your mac or windows computer?
Mac
I love the laptop hardware. The build quality of my laptop is much better than any windows laptop that I have seen. Price is comparable to business class laptops which is the only level of windows laptop I would buy. Consumer level laptops are made with marshmallows - so even though you may get a more powerful computer, they tend to break in 3-5 years.(always there are exceptions)
Multi-touch touchpad. I never liked any of the mouse interfaces on a windows laptop. The multi-touch trackpad and better touch tool means I no longer have to attach an external mouse to use my laptop. Hands down the best way to use a trackpad.
Time Machine - proper backup software built in and easy to use.
Windows
I can build a desktop computer for half the price and double the compute power of a Mac Pro.
Games, Games, Games.
Linux
Free! Ability to compile your own software for your own needs. Pretty much all engineering software is available for Linux. Running a server for just about anything(ssh,ftp,web,etc) is free and (relatively) easy.
2.) What are some pros and cons of each system?
Mac
Pros
Hardware/trackpad as stated above
Low count of malware
proper user accounts
iLife comes with the machine.
Great software like Quicksilver, better touch tool, Parallels to name a few.
Able to still run Windows with bootcamp or parallels.
Some Steam games are now available
Cons
Finder is pretty weak for managing files (one can claim Mac doesn't need file management as much as other OSes)
Docking stations for laptops are 3rd party and not that great.
Some software used in enterprise is unavailable native on Mac (you can run virtual machines or bootcamp to get around this but that means you need better hardware to run all those VMs, or a reboot)
MS Office - if you can live without it good for you, if you need to use it - it is just different enough from the PC to **** you off and until VBA comes back any complex documents won't come through correctly.
Entourage Sucks
Upgrading certain parts may void your applecare.
Windows
Pros
Your company probably supports it better.
MS Office has VBA
With Vista/Win7/IE8 maleware count has decreased
More compelling games available
Hardware choice
Yes there is a lot of junk software but there is a lot of very good software for windows.
Outlook is very good groupware
Windows Explorer has become quite good to manage files.
Cons
BS that they charged you for a new OS (windows 7) when all they did was fix the disaster that was Vista.
Still a target for more malware
Linux
Pros
Free
Software source is available for modification
Cad/Cam software
Server software
Free alternatives sometimes better than commercial software (Apache for example)
Cons
Support is usually on the web on forums/email lists - meaning you have to do the legwork yourself.(Some could say this is a pro)
Free alternatives not always up to sunff
Software availability
3.) Why do you not like other operating systems?
See the cons above
4.) Anything else to say...
Mac's build quality and support is quite good. This is because they make the hardware and OS so there is no finger pointing.