I never watched SG1. So never having seen the human form replicator episodes, I don't have that context to place this episode in. I have mixed emotions about the intoduction of this new enemy into the Atlantis universe.
On the one hand, I think they managed to make the Replicators far more creepifying in this single episode than they have with the Wraith in 2 plus seasons. The scene with Niam floating in space looking down on their planet was seriously creepy. And the Terminator-style walking through walls thing was pretty creepy/cool.
On the other hand, it doesn't seem like a good idea to introduce another set of "bad guys", when they are already pretty screwed fighting off the first race of villians. The show already has a little case of ADD, we don't need to lose even more focus than we have already. So unless the show manages to find some way to wrap Replicator and Wraith story lines together, I don't think it was overall a good decision on the parts of the writers.
To nitpick about the episode itself:
*Maybe I'm gullible, but I totally bought John's mental probe scenario. I was seriously clutching pillows. Rodney's insistence that John let them flip a coin to decide which of them should die would have been a great moment if it had been real. Well, its still a great moment, because I'm assuming those scenarios were supposed to put the person at their most vulnerable, and its very telling that Atlantis getting destroyed is John's worst nightmare, and that he doesn't think Rodney would let him "go down with his ship" without argument. He does seem to think everyone else wouldn't have that much of a problem with it. Even Ronon, which I don't buy. Boy's definitely got abandonment issues.
Also, did you notice how much more functional the team is in John's head? I wonder if that's the way John ideally would like them to be, or if that's how he honestly sees them functioning on a day to day basis? If so, he's a little delusional.
*Did any one else notice that we conveniently only heard about Ronon, Rodney and John's scenarios? All Teyla says is "That is not what I remember." And Elizabeth doesn't say a thing. *sighs* Way to develop your female characters, guys. Yet another example of the women getting shafted. *kicks writers in the shins*
*I know they have no budget, but the obvious re-use of the Atlantis set kept jarring me. Although it did allow them to do that awesome CGI pull away shot of the replicator's Atlantis, so I guess I can't complain.
*John has been on edge and bitchy towards Rodney this entire season, and it's starting to annoy me. I wish the writers would get John some meditation classes or something, and let him calm down.
*I'm not surprise that they completely screwed Niam over, but I'm still dissapointed. I'm glad/creeped out that Niam is still alive, because its anyone's guess what being sucked out of an airlock will do to his opinion of the Lanteans. I have this image of Rodney suddenly waking up in the middle of the night realizing that Niam is still alive, like someone realizing they left their oven on. I hope someone realizes this, but I doubt it.
Overall, it was a pretty good episode, although not the greatest. It seems like even the episode lows of this season so far haven't reached the lows of last, hopefully this will remain the case for the next 15 eps.