First, the good stuff - the relationship between Odo and his mentor, Dr. Pol, is genuine and touching. Given that Dr. Pol is already part of Odo's backstory, there's none of the contrived feeling we sometimes get when a "long lost relative we've never heard about" arrives in a character's life. The opening with Quark is nice as well - Quark's superlatives for Odo seem sincere.
The scifi story just left me shaking my head. Yeah, it allows Odo to take out some of his resentment at Dr Pol. But despite some twists it never takes off and barely makes sense.
The hints at Odo's heritage would of course get fuller airing later in the series, but here they are quickly forgotten once Odo becomes a monster.