(If you have not seen this episode you may want to refrain from reading any further, as this review contains spoilers)
The episode is centered on Kowalsky, showing us in a systematic fashion the changes that he undertakes as the goa'uld parasite within him vies for control. The result is a very fast paced episode that leads us successfully to the dramatic conclusion.
The most important aspect about the episode is the great bond between O'neill and Kowalsky, on which the writers have been working on in the pilot as well. The lines changed between the two are quite few in number, but they are well enough written and played to make us warm up to the tragic ending. From the moment O'neill recommends Kowalsky for promotion in the pilot (joking that he had a moment of weakness) there is obviously a great attachment between the two. Kowalsky has the heart and spirit of a young cadet in a way, his energy and dream of commanding a team perhaps being similar to that of O'neill's himself once. The fact that most of Jack's other teammates in SGC are scientists, makes for an even better reason to see in Kowalsky one of his best friends, with whom he can best identify. Following this line of thought, from my point of view, O'neill's joke about the stereo is the true climax of the episode. It's the last conversation between the two, because as the colonel will later recount, his friend died on the opperating table.
Apart from Kowalsky's drama, the epispode also shows us a little more on how "the goa'uld work". Impudent as always the goa'uld will not even consider a negotiation, the word "demand" being one of the few in his dictionary. A thing that ultimately works excelent, and the word-war between the general and him representing some strong plausible writing.
Last but not least, Teal'c also proves himself and joins SG1. His proud, upright stance, with the stargate glowing behind him, as he challenged the goa'uld was also a very nice touch.
So, drawing the line this was a very good second episode. The tension was just as high as in the first and from many points of view this can be seen as part 3 of the pilot.