Nerve is probably one of the more interesting episodes out there, as the new villain factors in to the show in a variety of ways. I like Scorpius a lot, and definitely an interesting way to introduce him.
D'Argo's reaction to Aeryn was one that I always found interesting. Despite his mistrust of Peacekeepers as a whole, there is still that warrior code that D'Argo respects, and he recognizes a similar warrior ethos in Aeryn. He may not always trust her or her judgement, but I think his softening towards her is a recognition of her as a warrior.