I love love LOVE the show, but hell, I'll admit that certain eps arent up there with other ones. Shindig, Safe and Bushwhacked are my least favorite episodes of the show, but you'll still find some great characterization in them. Our Mrs Reynolds is hilarious and awesome, as is Jaynestown.
Now, when you get to the third disc from the DVD set, if you dont like any of the episodes on that one, you are not going to like this show at all, and I'm surprised you even liked Serenity to be honest. Out of Gas is fantastic, and Ariel does start to set up the back story (even if said back story doesn't lead in to Serenity with a nice little bow).