Quark and Odo actually have a grudging respect for each other, even friendship of a kind. This has been seen many times before and after, but this was the one and only time their relationship took to the forefront of the episode. Really, I think their relationship works better in all those other episodes, where it's just a side plot, and less so here, where it's the focus. This episode was just too formulaic and predictable.
Seems like Odo's getting tired of his humanoid body. He's so much more irritable in this episode than normal. I think he's moved beyond his initial infatuation with the body, like ingestion. Maybe what he's really pissed off about is realizing he won't be able to go back to his people.
Nice to see Nog back. He's really throwing himself into the "image" of being a perfect, clean-cut Starfleet officer. But it's also nice to know that that doesn't last. He will grow up to the more realistic reality in later episodes.