I'm still curious about this supposed character development that the other companions got in the first couple of episodes that Amy hasn't?
I do actually wonder if people aren't mistaking RTD's (let's be honest somewhta lazy) trick of giving the character a lousy family situation for actual character development? By the end of The Unquiet Dead I doubt we knew that much more about Rose than we discovered in "Rose", well aside from her liking chips and having watched Newsround at least once. As for Martha, well the only character development we got from her was her wuv for the Doctor. Seriously if people think a character can only seem 3D in relation to a harriden mother then they need to watch more tv and films!
The only companion I see as really changing in the first few episodes is Donna, especially after her encounter with the Ood, Donna grew over the course of her year with the Doctor, I'm not sure Rose really altered very much at all in two years, aside from getting a bit cocky, and Martha remained a simpering love struck puppy from the Shakespeare Code to The Sound of Drums, only changing in Last of the Timelords.