Yikes. A little spoliery here. Ah, well. I can't stay ignorant forever, I guess.
My frame of reference is just the first season. I've really liked Rose, and I find her quite appealing, although I can gather why some wouldn't.
We've mentioned how Eccleston was a good "transition" Doctor--I actually think he was better than that, but that's just my assessment--but I think it's interesting to consider Rose as a kind of "transition" companion for the Doctor. I would say that in the classic series, companions were almost always (except for the companion *you* really liked, of course
) more or less plot devices and exposition expounders. Some stayed for a long time (Sarah Jane, e.g.); some came and went rather quickly; but for the most part they all served to highlight how cool the Doctor was, to get captured, to ask the Doctor questions that the viewer might have, and so on. Seems like we rarely learned much about any of them. We might've known Leela's "savage" background, or that Ian was a schoolteacher, or that Ace was a bit of a rebel (just to cover the gamut here), but they seemed more like static characters, if you'll forgive me, frozen in time. They rarely developed much--they often were just the same the last episode they were in as the first one. (OK, of course there are some exceptions here--Turlough's probably one, and Adric obviously had something happen to him, but I think the general principle holds.)
Like it or not, Rose has probably gotten more character development than all the classic series companions combined, and she's emerged as a character in her own right, not just a plot device. She's helped develop the Doctor's character, which has seemed more mutable than earlier Doctors, and it's felt like she has an interior life; she's not just an extension of the Doctor. I, for one, have been more than glad to have her around.
