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.
Hey, good to see you over here from the sinking ship of ST.com's forums!
On subject, the Ascent was a good episode in a number of ways. The plot itself is predictable, but what sells it is the interaction between Quark and Odo. If you put say... O'brien and Bashir in this episode, it would have fallen very flat. Those two are just fun to watch and you get some good character detail on the two. Their love/hate relationship is just enjoyable on so many levels.
Nog's return, also cliche, but you can deal with it. You knew he'd be back at somepoint. The story between him and Jake was mostly filler, but it does show how much Nog has changed from the bungling thief we saw in Emissary.