Short story: if you appreciate swordfighting games even in the slightest, this is the game to get to fulfil that.
Long story: combinations, skills, appearance, community.
I will summarise basically everything in this game, so you might consider it spoiling, but this sort of game doesn't have a story mode nor secret things (as far as I know)(yet...).
If you want to know, some or all terminology I use here is made up on the spot, but makes sense.
There exists a tremendous amount of combos, due to the different features of a sword strike that you can combine. There's the usual light/medium/heavy attacks (delivered in the form of 'stances'), and each wieght of attack having its own string. But this game brings in charging attacks (not running in, but hold to power up), side movement modifier, other side movement modifier, and even aerial modifier, with complete freedom of flow from one piece of combo to another piece (save for string in weight). In addition, there is blocking, grappling (don't worry not spam to win), and parrying.
Each character (only four) has their own move set. There are five types of sword: longsword, katana, rapier, jian, scimitar, each with their own stats and 'block' tehnique. That is, the mouse right-click is the generic button for alternative sword use, with most sword types providing an actual block, but some only a 'guard', fient, or deflect.
Other than that, there is knowledge and skill - oh, and appearance. It is very much a skill based game, but obviously learning each character's set of moves helps a lot. As for the aesthetic side, graphics are good (I always run at minimum on games like this so as to minimise slow down and lag), maps are great (especially the free for all maps), and the Workshop is widely used to create new swords (not new types of swords), new maps, and new character skins (all free and easy to get your hands on). Oh, yeah, and great soundtrack that really fits/sets the game style.
The community is very good. Lots of helpful people who value chivalry and honour. Admittedly, I have only played during the free weekend (weekend), but the non-free weekend (weekend) players were obvious compared to the free weekend (weekend) players, due to ranking. Gosh, that was a mouthful.
And that's it. Very much arena fighting game (1v1, 1v2, 2v2, FFA, Capture Points) with an elegant combat system. So, not quite worth full game price unless multiplayer is your focus in games. At 75% off though, I think everyone should get it.