Agree completely, & Ubuntu has even been compiled for Raspberry Pi so you can run a full desktop on a dirt cheap system of total cost (system, case, mouse, keyboard, PSU, everything but the display) <$100, easy.
I've used Linux for a number of applications in the workplace, including running fullscreen displays of Grafana showing Zabbix data for critical servers/services, as digital signage running image sliders, even as a Ubiquiti Unifi Controller. And everybody loves a 
RetroPi or XBMC/Kodi Linux media server box.
But you should mention that some commercial applications and games aren't available on Linux, like MYOB or a lot of AAA games, so a dual boot or investigating switching to alternatives/substitutes will be necessary.
Just show them Mint MATE with a hck3r wallpaper & conky - they'll be all over it :P
Well I'm not a gamer so I couldn't care less, for me it's very comfortable. If I really wanted to play some games I'd mostly play retro games that is what I have grown up with, all those arcade games in the 80's, I am not really into the computer video games. Most retro games do work on Linux, like the old Nintendo games, there is a Linux emulator for that.
I like that wallpaper with the girl. But in reality there is no need for fancy desktop, I personally couldn't care less about GUI, so I am for performance not design.
It wasn't a criticism or a suggestion of what you should do with your system, just salient points for others to consider.
Most people care very much about the application they run their business on, their library of computer games, and some spend more time customising the appearance of their GUI than I do setting up a Debian server.
I've a Pi with some nice old ROMs on it, been meaning to see if I can get some old skool C64/Amiga running on there because I no longer have either system or the library of software for them that I once did, but neither do I have the time to play games much these days.
Glad you encouraging people to try Linux, truth is that several recent Linux distros are quicker and easier to install than Windows.
Mint can be installed in 10 minutes, totally clean install, by removing every other OS in the harddisk.
It has very easy instructions even a grandma can install it.