This was the best episode of the season, including the ones with Gibbs. There were ties to prior episodes this season (including several mentions of Gibbs), and every regular on the team had a strong role and great performance. Even Ducky had a lot of airtime, despite not being in all the episodes this season.
Parker became the central player and they developed his back story a bit, but the team was also very important here. It was pretty cool to see Parker's residence, and Kasie had an interesting connection to Parker with her interest in plants (Kasie has become a good quirky replacement for the quirky Abby).
If NCIS were to have another season (apparently they will), Parker's character had to be developed, so that was accomplished. He's not Gibbs, but that doesn't mean the show won't be interesting. They left the episode on a cliffhanger; I'll be looking forward to next fall's conclusion. Next season has a lot of possibilities, maybe bring back DiNozzo for a guest appearance, etc.
I agree with other reviewers that the Jimmy & Jessica romance is not a high point. Then again, it's not a huge negative for me. I didn't see the hint that Torres might be leaving (that someone mentioned); I hope not, because he's become a prime character, and provides the "macho" element that Gibbs used to bring, although Jessica provides some of that too. There are so few decent shows on tv today, I'd hate to see this one end. Keep it going! Mmm...kay? If you could do that, that would be great.