I’m a big fan of Order of the Stick, but I really felt that the plot got derailed after the fall of Sapphire City. The party was split up in two or three places, there were too many subplots, and too many intrigues involving minor characters that I didn’t care about. And the big picture plot with Xykon seemed to get lost in all of the noise.
However, the recent Evil Vaarsuvius arc has been plain awesome. We’ve gotten major development of one of the central characters, tied up a multitude of loose ends that have been lying around since, well, since the fall of Sapphire City, and it’s actually been funny. See the linked strip for demonstration of awesomeness. (But note that this isn’t the beginning of the arc. You’ll need to go back 15 strips or so to catch it from the start.) I anxiously await the conclusion of the arc.