I'm a bit worried about Joan of Arcadia -- it's been getting somewhat complacent and lax in its storytelling and content. A couple problems spring to mind. First, the relative lack of theology (excepting the first episode and select others) has led the show to dangerously close to being a safe (i.e. boring) exercise in "one tiny thing leads to another"-ism. In an effort to present an all-faiths encompassing deity, the show sometimes handicaps itself from offering more effective meditations and explorations of the relationship between a person and God. When JoA gets into the nitty gritty, though, as in the episode where Joan visits Grace's rabbi father, its potential is far greater, but in that very episode, the pacing skewed away from the possibility of the being speaking to Joan as a devil and towards interpersonal melodrama.
The second thing is aesthetically related; its family-oriented nature, combined with the Fat Tony storylines, is particularly jarring when done well and ineffective when done poorly. Will's job in the police requires a darker tone that clashes with the high school drama of the show, but when the show shifts to one of his more existential moments, it can be crassly superficial and hollow (e.g. the last episode at the spa) -- especially if the setup has been light-hearted.
Another point, somewhat unrelated to the other two, is Grace Polk's role -- in her cynicism and (relative) maturity, the writers have made her into a narrating figure who tells both character and audience what just happened and what to think. And seeing as the show is supposedly about God, doesn't quite work out well. (Not to mention this arrangement being lazy storytelling.)