I have used linux only for 2 years and even though it wasn't always that smooth, I loved it none the less.
* The first thing that really attracted me was the amount of customisability available in linux. Even though I don't customise that much now but still the ability to change certain things is very useful.
* Even though windows has virtual desktops, its implementation on linux feels much more solid.
* My trackpad feels more fluid and natural on linux.
* The filesystem on linux makes more sense than on windows.
* There are some really great software on linux and a lot of great cli softwares.
* Terminal is excellent for getting work done and it isn't that scary.
* There are a lot of desktop environments available (my favourites : budgie,lxde)
* Works great with my potato systems.
* Excellent for development.
* If we can ignore the fact that there are so many package managers, the entire system of package management was just mind blowing to me when i first started using linux.
* Security on linux is really robust and that is not because people don't use it. The general practices on linux is what makes it so secure.
* Linux is case sensitive and doesn't care about file extensions. These is something i really like.
* The ability to install different shells.
The thing that I don't like is, sometimes i really don't feel like reading through a wiki to get something done. But that has nothing to do with the os and more with how people package their software.
There are a lot of small things that make it so enjoyable and useful. One has to use it to understand what makes linux so beautiful.