Update 2: I want to strongly enforce my opinion, that if you are looking into buying this game, the main reason should be Obstacle. While you can play other modes with friends or from time to time with strangers, obstacle is always playable and has a great variety. There are servers for tutorials, puzzle maps, different difficulties, dumb maps, progressive maps and coop maps. I started playing to play this game again around February, and played several hundred hours in quarantine, most of it in Obstacle. See this as the Trackmania of the Ego-Shooter world.

Update: Around 400 people play this game every day, and finding a game is generally not a problem, at least in the evening and if you join the recommended game mode of the hour. Also, Obstacle is probably the best (singleplayer) movement based ego shooter gamemode of all time and the game is worth getting just for that mode (the learning curve is steep though).

+Easy to learn, hard to master.
+Modes are fun and I feel that some of them are unique to Shootmania.
>+You can also programm your own modes with Maniascript.
>>+People programmed modes you can play alone like Obstacle, Survival etc.
+Integrated map and replay editor.
+You can customize your crosshair, player model etc.

-Low player base, those who still play should easily outplay you if you are new.
-You can only choose your crosshair and player model in game. Importing it so you can choose it is something you have to figure out yourself.
-UI generally is not very intuitive.

-->The gameplay and possibilities are great, thats why I give a positive review. But the low playerbase is a huge drawback for new people. Try the free demo, it lets you play the game almost unlimited. In case you like the game after trying it, consider buying it to show it some love.