Anybody ever played one of the .hack// games?

After watching the anime series called hack SIGN, hack DUSK and hack ROOTS I started loving that "The World" thing, and I bought the first game, it's really interesting and enjoyable to be able to walk around, fight and everything else in the same world the characters of .hack anime series are.

At the moment I'm still at the first one, hack INFECTION, I'm currently dedicated on getting more Virus to hack forbidden zones and get more information about that Ryu Books (I know I could simply search a guide about the game, but I prefer discovering everything by myself).

Which games of the saga you've played or you're playing? What's your opinion about .hack games in general (and the whole hack project)?