I actually started the series with Brothers in Arms/Mirror Dance, which helps -- Miles is slightly less hyperactive as he ages, and Mirror Dance is the chronologically first of the 'books containing Miles' that has a second narrator. (Mirror Dance also has Aral and Cordelia and marks a noted shift back to Barrayar that really is cemented in Memory, the next book.) I think I wanted to shake Miles a bit during TWA, but mostly because he was being an eighteen year old boy who had more intelligence than real-world experience. I probably wouldn't have noticed this reading it at fifteen.