PS+ is awesome. You also receive bigger discounts on sales for games and in a lot of cases exclusive sales just for + members or other perks. Also for the PS4 any F2P games you play as a PS+ member will give you added content to that game.
The games they are giving you day one on the PS4 with PS+ are Resongun and Contrast, both look very good.
Every month they will be giving a PS4 game to PS+ members and PS3 and Vita games as well.
Here is a list of the games they have given away so far with PS+
http://en.wikipedia.org/wiki/Instant_Game_Collection
Each week we get new games and when you first sing up you get what they call the Instant Game Collection with is about dozen games for PS3/Vita currently.