I played Secret World during the beta and in the early-access period.
I won't dwell too long on the setting; all the myths of mankind are true and a trio of secret societies have put their differences aside to tackle a rising darkness in the world.
I've played a lot of MMOs (Eve, WoW, LOTRO, Tera, WAR, Rift, SWTOR) and The Secret World is the first one since WoW to really suck me in. It's not like any other MMO I have played.
Funcom have developed a leveless, classless style of play where a player has over 500 skills to choose from, but can only use 7 active abilities and 7 passive abilities at any one time. The abilities they equip define their role. It is hard to describe just how well this works. As you progress through the game, complete missions etc, you unlock ability points which you can accumulate and spend to give your character specific abilities. If, at any point, you begin to regret your choices, you can simply begin investing points in other areas.
The combat feels solid and mobility can be crucial, which gives the game a much more actiony feel. The settings in game are particularly well-executed and it is evident that this is a labour of love.
There are somethings newcomers should be aware of. If your background is from WoW or one of its derivatives, where everything is sign-posted and your hand is firmly held throughout - TSW does not follow this. There are a number of different mission types, one of which is Investigation. For this you will be tasked with tracking down information using loose clues, your knowledge of the local game area and the in-game browser. The game actually requires you to think. I've seen a lot of people just asking in general chat for answers to riddles or codes. If that is your default way of dealing with challenges in an MMO, then save you money and skip this game because you won't enjoy it and the community will react badly. Also, there is none of that respeccing nonsense. If you go deep into pistols and then decide you don't like it, you can't refund your points and invest them in, say, Blood magic, you need to start from scratch. While this may seem alien, it makes sense as eventually a player will have every skill and be able to fulfil every role. But, again, if you want instant gratification, TSW is probably not for you!
Also, there is no world pvp. It doesn't fit the lore and this was a conscious design decision on the part of Funcom. For one, I am glad as in most other games 'world pvp' simply means 'ganking'.
Personally, I think this is the most refreshing MMO I have played in years. The missions are filled with both humour and horror, and there are a lot of references to real life cultural signifiers as you travel through the world. The character customisation options (beyond the character creation which is, admittedly, limited but due to be improved) are so very numerous. I can't recommend it enough and if you are looking for something beyond the usual, check it out.