I played Sm4R on Ubuntu via wine without any issues during the beta phase.
The game ingeniously combines tons of RPG and hack'n'slash elements with a very dynamic world that feels more MMORPG-ish than actual MMORPGs. The humor is on point and the bots are hilarious. They won't hesitate to call you a noob and laugh directly in your face when you mess up.
You can gear your character in many different ways with the insanely rich selection of items and the shiny auras and mounts you get will make you feel epic... till you get one-hit by entering the wrong area.
Explore for riddles, battle bosses, survive in an arena - but don't be afraid to die, because you actually get a visit from the Grim Reaper which is my favorite visual effect in my game. Speaking of which, the art style is as unique as it can get and matches the grotesque setting perfectly. :)