This is a very rules-lite generic roleplaying game and it does what it says: it's unbelievably simple. There are some optional rules to make it more "advanced" but in its heart it is still a very leightweight system.
The rules are clear and intuitive. (Which is a good thing! So many games use "innovative" rules but those hamper gameplay if they are not logical in a game sense.)
You have 4 stats: Action, Wits, Ego & Hits. You divide an array of d6, d8 and d10 between Action, Wits & Ego. Hits are derived from rolling your Action and Wits trait.
Every character gets three specialisations which are tied to either Action, Wits or Ego and round up your character.
The resolution mechanic is binary: you need to roll over a difficulty rating to score a success. Contested actions are resolved by comparing the roll of both parties.
Combat is also quite straight-forward. Both parties roll their Action stat and the difference reduces the Hits of the loser. Weapon and armor may give bonusses or penalties. You may use specialisations in combat.
And that's it mostly.
Players will find the specialisations and the optional rule of narrative points useful for customizing their characters. Nonetheless, USR being a rules-lite game, much depends on fleshing out the character with narrative details instead of mechanical traits.
There is not much of a GM section in this short pdf. However, I don't mind because who of us is still a beginner in rpgs? :-)
I would have liked to see a small section on how to create opposition. On the other hand you can just devise opponents on the fly as the rules are fairly simple. (The free setting Halberd has some suggestions if you are interested.)
There is not much to distinguish it from other lightweight roleplaying games like Folklore, Dime Stories or Pulp! EXCEPT the support you get from the author and the community. At the time of writing there is a webzine, a solo adventure, a tongue-in-cheek-fantasy setting I heartily recommend, a mini-adventure and a cyberpunk supplement. Furthermore, there are some other gamers who are adding material like a Sword & Sorcery adaption.
So I can recommend it if you are looking for a very simple and easy game. There is nothing fancy but I favor it over the above mentioned alternatives because of the support material. Check out the google+ community for more stuff:
At its core it is very tradtional in the sense that it uses a binary task resolution, no descriptive traits or other abstract means which became popular with the rise of games like Fate Core.
Because I'm a fan of those characteristics I give USR 4/5 instead of 5/5 but that's personal taste. All in all, the game does what it says. And it's FREE!