Her design is amazing. She is attractive, yet the design does not follow the idealized (in many cases outright sexualized) "beauty" pattern established by the industry, which is refreshing and very, very welcomed.
The voice acting is amazing. Ashly Burch really nailed the character and her performance was outstanding.
The writing is incredible and the story behind her is fascinating. John Gonzales just cemented his place as one of the best writers in the industry with her character (and the overall game story of course, which is amazing, especially for an open world game).
Her gameplay controls are fantastic. She is super responsive, yet there is an incredible amount of high quality animations for all her movememts, which makes the responsiveness and fluidness of the character even more impressive. Summarizing, she is a joy to control, and considering the clunkiness of character movement in big AAA open world games, it is definitely something worth pointing out!
All in all, I loved everything about her and I am starving for more Aloy already!