One of the reasons I love Doctor Who is because it has a plethora of strong female characters. Such as Amy Pond:
Amelia - Amy - Pond. Newest companion to the Doctor. I liked her first off because she was so brave - even as a kid she wasn't put off by this mad raggedy doctor man. As an adult, she whacked him over the head with a cricket bat and then slammed his tie in a door! And I liked her because she thinks like the Doctor, which was demonstrated in episodes one and two (as evidenced the weird filming techniques). Brave and intelligent!
All that, of course, are only components of her most amazing quality: her self-assuredness. She's not afraid of her sexuality, which I really respect. I find it utterly refreshing that, though Amy is sexual (more so than the other companions I think, as evidenced by her snogging the Doctor and wanting to snog him later), it doesn't define her. She is so much more than the female companion/eye candy - she saves the day, she understands humanity in a way the Doctor can't because he's not human. She's bold and daring, insatiably curious (which isn't shown as a "bad" quality or fault -- ie, curiosity killed the cat, the Eve syndrome, etc).
From a slightly more English-Student point of view:
1. She's not a damsel in distress. As a woman, she's not there to be protected.
2. She's not the prop the big wigs use to say: Look at this cool woman who is so bad ass and not at all stereotypical. Let's make sure everybody gets it by having other characters (or even the female character herself) marvel how a woman could be so awesome (Butcher, I'm glaring at you). (I think the only show I've seen that actually pulled this off with any amount of success was Stargate SG-1, when Samantha said something along the lines of just because my genitals are on the inside than the outside doesn't make me less than any one of you or words to that affect.)
3. She's complicated. She's not just there to support the Doctor (though she does support him as he does her) - but she's on her own journey as well. She's grown as a character from the first episode to the last episode: in a nutshell, before she was running, and now she's not.
Like with Donna and Martha, the Doctor and Amy and even Rory are equally individuals and their relationship together fosters that instead of inhibits it. It's not like she has a gender role -- she's simply, beautifully herself.