I'm not going to argue against someone who would describe The Leftovers as tedious, however I will say that there's a lot of good things there. My only worry is that people who watch the show but have a lot of criticism are jumping the gun a bit. Given that Lindelof is involved, people are probably going to compare the first season to how LOST eventually turned out. I don't mean that in a negative way necessarily, but it's obviously going to be negative for the people with similar problems.
I think there was some payoff in the last few episodes, especially the last one. There's been a rather slow buildup, but there's obviously something going on behind the scenes and it'll probably come to a head in the last few episodes. The spiritual/supernatural element is pretty nuanced and not quite in your face. I'd compare it loosely to the Left Behind series. I only read the first book, but something like this is way more interesting to me. It isn't trying to be preachy and a lot of it is left up to interpretation. Aside from the religious imagery, we're not even sure whether October 14th was even The Rapture in the first place. The concept is a lot more realistic to me.
I haven't read the novel, but I found it interesting that it's a single book, so if it's extended (which it looks like it could be) for more seasons, how much material is left to actually adapt.