Yet another episode to start off with a bang. Firstly you have such a huge attack sequence on the planet (although why is the Stargate near a body of water, where the ground could erode or get flooded?), and then we see our beloved Carter get possessed by a Goa'uld! (Which was very well shot and executed.)
It's hard to imagine how I would've felt at the time I first saw this, considering I was about 12 or something when I got into the series, and I know all to well now what will happen. But still, I can imagine how much someone new to the show would worry about the fate of Carter, especially since for all we know the Goa'uld are all evil, and especially after what happened to Kawalsky...
But, as all us fans know, this is the point where the Stargate mythology gets a little thicker with the introduction of the Tok'Ra. We are skeptical at first, but through Jolinar's sacrifice we realise he was being truthful the whole time, and sympathise with him. His sacrifice is more impactful when you realise that it may have been so we would see the true nature of his race, and to show us that they are worthy allies.
One could argue that the last few scenes with Carter's emotional turmoil are either emotional or sentimental, but they still pack a punch. Also, the interrogation scenes with Jolinar, in particular the one with Teal'c when Jolinar claims to be a Tok'Ra (and Teal'c reaction), are very entertaining and effective.
In summary, this is a 100% must see for any soon-to-be SG-1 fan, and I'm sure they'll love it (or at least like it).