All the feedback I got is quite positive, so I finally decided to buy it and give it a try.
Apparently if you are looking for a revolutionnary pvp, the game is not for you, its pretty standard stuff with backgrounds and arenas. It is not the "big thing" of the game. But if the combat system is good, then pvp should be, though, at least.
Otherwise, the combat system, I will have to try it to see how it is. People seem to say that it is quite slow/clunky at the beginning, and starts to improve a lot over time. Pve donjons and raids apparently have been described as very well constructed and thought, though there is nothing revolutionnary here either. On the good side, you can custom your skills the way you want (just read any guide on the matter to understand how it works, it will explain it better than me).
The character creator is my only fear, it is really basic with not many choices (except for clothes, it does not really matter since you can get/buy a lot of clothes once ingame).
On the good points though, the feedback I got was that the universe is very, very, subtle and well written. The story is quite engaging and also adult, with very deep NPCs dialogues, and the solo quests all have their little unique and immersive cutscenes. It is worth mentionning that not that many quests will actually ask you to farm mobs over and over. A lot are about investigation, clues to find, enigmas to resolve, and when that happens, you will have to do it alone since the game does not bring you the answers. You will often have to look yourself on the net (I friend even opened his bible to find an answer to something, he told me). Exploration specific quests will not even points you the direction, you actually have to find it. There are also infiltration missions ala Deus Ex where you have to remain unseen.
Then, you have the "sandbox" part of the game where you can learn every skill, and get the appearance you want, with the clothes you want, and the weapons you want. Maps are described as gigantic, and yet not generic and void of everything at all. There are a lot of little things that make players pay more attention to what they do, for example I have heard that if you jump on the abandonned cars in the streets in the first area, it will trigger their alarms and attract all the zombies around waiting for the feast. Or, a friend that saw a steel-jaw trap on the floor, thought it was just part of the scenery like any standard prop, walk on it, and almost died hemorraging all over the place. Though I am slightly annoyed that falling from a certain height does not kill you...
Amongts other things : a crapload of emotes (I am looking at you SW:TOR), devs that say that they are definitly interested to see RP blossoming in their game, devs already mentionning possible housing, etc.