I'm a little of tired MMOs trying to implement "stealth." I love stealth games. Stealth-action is my favorite genre, in fact, but I have never been a fan of just turning invisible. It is so lame to me. I prefer the stealth challenge to come from having to carefully watch a guard's head movement to determine his field of vision and then to silently sneak up from behind. Obviously, that type of play doesn't lend itself well too an MMO, but the turning invisible effect is just so lame and overused. It doesn't make me feel stealthy.
Okay, I know GW2 will probably make it more fun than the way it has been implemented in other MMOs, so I will withhold further judgement.