In general terms, this follows the pattern of a "bottle show", even though the story doesn't take place in a confined location. Instead, it largely takes place in a forested area. With some clever redressing and camera work, a very small wooded area can look rather large, so it's possible that the same budgetary concerns were in play.
The point is that "bottle shows" are usually a means of saving money by forcing selected characters to overcome a problem of survival. The plots are typically very simple, forcing the writers to use character development and conflict to drive the episode. The results can either work brilliantly or reveal weaknesses in characterization.
In this case, Teyla and Dr. Keller are trapped on New Ethos, the planet where Teyla's people took up refuge. The Ethosians are missing, and all the signs point to a tribe called the Bolokai, savage cannibals that have been enemies of the Ethosians in the past. Teyla and Keller must take to the forest to survive, and each handles the crisis better or worse.
Teyla has the opportunity to shine in this episode, even though her personality becomes dominated by the warrior aspect, thanks to her anger and desire for revenge. She is convinced, for much of the episode, that her people have been killed. This leaves her with the desire to survive and avenge, and it brings out some of the darker qualities within Teyla, the ones that have been largely suppressed since her initial appearance.
Dr. Keller, on the other hand, is saddled with overly-familiar characterization. Keller is quickly hurt, and she is convinced that she cannot survive. Keller descends into a mixture of self-pity and whining that is nothing short of McKay-esque in nature, and equally tiresome in large doses. It's quite predictable, especially when Keller eventually overcomes her fear in the final act. Thankfully, her efforts are only mildly effective, and salvation comes from a rescue team from Atlantis, not some sudden onslaught by Keller herself.
The positives for Teyla are counterbalanced by the negatives for Keller. Similarly, others aspects of the episode balance out. The disappearance of the Ethosians gives Teyla a character arc of her own, something that has been sorely lacking over the past couple of seasons. On the other hand, it is revealed that Teyla has been having a relationship with a fellow Ethosian recently, one that has become rather serious. This is a completely new plot element, and one that seems to fly in the face of the relationship that had been building between Teyla and Sheppard. This is very likely the method of incorporating Rachel Luttrell's pregnancy, but it does seem to come out of nowhere.
In the end, this episode finally provides Teyla with a solid character arc for the future, but the questionable choices for Dr. Keller represent a disappointment. If the writers use this as a starting point for Keller with the intention of building a longer arc, then future episodes may mitigate the damage. For now, the writers seemed to undermine the strength of the episode and Teyla's new direction with predictable character development.