Out of the female characters, she was my favourite after Tali. Jack was whiny, violent, out of control, and an all around *****. Samara was self-righteous, saw everything in black and white, and also completely out of control. Both of them annoyed the hell out of me.
Miranda, on the other hand, had great voice-acting, one hell of a back-story, stayed alive and was always useful in combat (and when I say always, I really mean always, unlike Tali), and betrays Cerberus for you at the end. She's ambitious, ruthless, brave, knowledgeable, pragmatic, and loyal, what else do you need? She wasn't just cocky, like Jack, she was confident in her own abilities because of experience. When she says to Jacob "I'm always right", that was more of a re-assertion of leadership roles rather than some stupid boast. In addition, Slam was such a great special ability I gave it to my main character.
On the downside, her face was really badly modeled, I don't know how they screwed it up so much. I found it funny how the best rendered faces were the alien ones (Mordin, Garrus, etc), while the human faces usually came out kind of blocky and weirdly animated. Her's was by far the worst, it got to the point where she was more endearing off-screen than when looking at her.
The other thing that really pissed me off (and somehow I thought Bioware wouldn't fall into this trap), was that she was wearing high heels all the time. I don't freakin' care if high heels in the future have in-built kinetic barriers or mass effect fields, they don't make sense on the battlefield. Seriously guys, what the hell? I thought we grew out of this crap, no one in Mass Effect 1 had heels.