They've always been foils, and the truth of it is that Rose, so far, has been rather intelligent. And since it obviously went over your head, I'll explain what happened in episode 2 for you (and I'll try to use small words):
When people are all of a sudden in very strange situations or different groups they get what is called "culture shock." This is what happened to Rose and it happens to people in the real world all the time. The fact that she was not only capable enough to cope ("You two go pollinate, I'm going to talk with Michael Jackson."), but she kept her wits about her (only one other companion ever noticed being able to communicate with aliens in English).
Personally, I thought the episode was great. It was as cheesey as Doctor Who has ever been, but presented so well that I didn't care. It was fun! I also liked the little jokes (the Ipod bit) and it had some good lines (the one mentioned above, f'rex). The metaplot bits are also good, as we get a bit more information about the war mentioned in ep. 1. I think there's a lot of rampant speculation that the Daleks were behind it (he avoids saying who he fought against in this episode).