If we're talking quality versus other subscription modeled MMOs, then yes, I would pay $14.99/mo for GW2. Needless to say, ArenaNet is developing a game that visibly outshines most current MMOs; the combat looks fluid, the environments are rich, and they're innovating in areas that other MMOs will not.
However, one of the biggest selling points for Guild Wars 2 is their no subscription model. If I'm thinking forwardly, I'm not sure that I would pay for Guild Wars 2; if the game grows as large as expected, it should lead the charge for non-subscription MMOs in the future. MMOs would be a lot more accessible if subscriptions weren't so common.