OK, my own thoughts. Warning: I'm longwinded. Deal with it.
Love it or hate it, this one was SG-1. As someone mentioned earlier, perhaps you can classify it as middle season SG-1, but it's still SG-1. Besides, any episode that makes all of fandom retreat to their respective corners sounds pretty classic to me.
I'm surprised to see so many threads about how Ben Browder and Cam Mitchell are being, pardon the pun, shafted by TPTB. As an avid SG-1 fan from the very beginning (wow, that was a long time ago), I've rather enjoyed his measured, steady introduction to the story. And I've certainly enjoyed the fact that Carter, Daniel, and Teal'c are being treated as the leads they are. It seems that a lot of Browder fans were expecting him to join the cast and immediately dominate storylines and screetime a la John Crichton, but SG-1 has always been its own show and about its four original team members. Lots of other characters join in the fun, but that the show is still predominantly about Sam, Daniel, Teal'c, and even Jack to some extent, makes me one happy fan. In his first episode Mitchell told Daniel that he wanted to learn from the best, and that's exactly what it looks like he's been doing. Like it or not, he has no experience with gate travel, with off-world politics, and with serious interaction involving aliens. Add that to the massive expertise of the other SG-1 team members, and the fact that at any given time they become de facto team leader is hardly surprising or unexpected or improper. Mitchell should certainly defer to Sam when dealing with technology, to Teal'c when dealing with the Jaffa, and to Daniel when dealing with cultures/history/artifacts.
Similarly, the fact that Mitchell is the team leader at all really seems to be a matter of casting/production politics rather than one of military protocol. His promotion to SG-1 is, perhaps, the biggest plot convience of the whole season. Certainly the return of Col. Carter, along with her massive experience with the stargate itself, her eight years of field duty, her history with the Goa'uld, etc., trumps any claim to command that Mitchell holds. And while I'm aware that often times the best person doesn't get picked for command, in this case the very nature of the Stargate Program kind of rules that out.
Oh, right, Ex Deus Machina.
Well, Teal'c emerges as the real standout in this one, continuing to fight for the well being of his people (both Jaffa and Tau'ri). His composure and patience in the face of defeat at the end of the episode illustrates how far he has come as a character. His reactions and his words are those that I'd expect from Bra'tac, and that Teal'c has reached that stage of maturity and experience is a satisfying journey to have watched.
Carter resumes her place with appropriate aplomb. She carries a good portion of the story in this one, and the inclusion of some personal tidbits help to establish a comfortable base for the rest of the season. It also appears as though her return also allows the writers to finally progress the story further, after holding pretty much pat for the first five episodes.
Daniel, despite a much deserved (and needed) break from the spotlight, manages to maintain a presence in the action. He looks quite at home cavorting about with Sam, and thankfully more relaxed without Vala around.
And, then there's Mitchell, who like Daniel, manages to maintain a presence in the story without having very much to do at all. His idea might have saved the day, but it was a passive solution, and one that doesn't really allow for a great character moment or tremendous screentime as hero. See above for my sentiments on this.
Landry continues in his role as Hammond Jr., not intruding into the narrative and not taking the spotlight away from SG-1. And Gerak manages to be an effective foil for Teal'c. Kudos to TPTB for not letting Lou Gossett's and Beau Bridges' famed status overrun the story and the show.
Lastly, Ba'al still holds his place as the most engaging Goa'uld since Apophis. His perpetual promotion of his own well being and his own agenda serves him well. I'm not too sure how I feel about the clones, but I said that about Replicarter too, and was forced to eat quite a bit of crow after New Order. I think I'll reserve judgement for a while this time.
I'll end with a few complaints. I like the Prometheus as much as the next guy, but the show could definitely use a break from it. The next few eps look to be going that route, so we'll see. And the bit with the building I can swallow. It's just a little rough going down is all. As for the real Ba'al, I'm hoping he wasn't on earth at all. There a number of explanations for the clones Goa'uldish nature, the easiest being that they weren't Ba'al, just other Goa'ulds who had taken his cloned host. Lastly, the patch scene was nice, but too understated for my liking. I'd have preferred more of a to-do over SG-1's reformation. And they still haven't resolved the command issue, one way or the other, enough for my tastes.
Still, I enjoyed it. Bring on Babylon.