After recently getting interested in Monk I think building a competitive monk practically requires the archetype and a vow or two for extra Ki points. You can use Qingong to get the Barkskin SLA so you don't need Amult of Natural Armor then use the freed slot for an Amulet of Mighty fists or just make a weapon Monk and use the money for something else.
Other archetypes also seem to be nice if you have a theme you build toward.
I always felt that Qinggong was essentially meant to be an apology for the core Monk, though no one in Paizo would ever say it that way. It's completely modular and optional, so it stacks with everything; I love it. Wish more classes had archetypes like it... but then again I guess most classes have that built in, see Rage Powers, Rogue Talents, Revelations, etc.