"What are the advantages of this operating system?"
Fast virus and malware free
"Can I have fun sharing my experience with others? Is there a community sharing emails, or a web page where messages can be exchanged?"
Linux distros are comunity made and supported, Each distro has a forum. Mint and ubuntu both have forums.
http://ubuntuforums.org/forum.php
http://forums.linuxmint.com/
Puppy Linux murga forum is good.
http://murga-linux.com/puppy/
"Is there software to buy, or free software to download?"
Most software is free to own and also free to adapt.
http://linuxappfinder.com/alternatives
"Can I test software, and report on it?"
Yes to the forums both distro and specific application forums or sourcforge site, Bug reports etc and you can adapt most code and programs.
Are there games?
Yes, some may take a bit of work depending on your distro
Mint and ubuntu have games in there software binary repositories
I use flight gear, simutrans and freeciv,
Softpedia is also a good place to look.
http://linux.softpedia.com/
for more specialized stuff
http://webscripts.softpedia.com/
Linux is not windows.
I view the difference as going from A to B in a car compared to a motorbike.
Both get you to B but the journey uses different techniques and feels different.
So the answer is that Linux cannot be compared to windows as its different in lots of ways. If Linux was the same then linux would catch virus and malware.