The gifted kids in our district, especially those who attend the gifted magnets, are strongly encouraged toward IB for high school. (This district is just adding the early years IB.) Our previous school district had early years when the youngest were starting kindergarten; I didn't look at it because the school itself had a reputation for punctiliousness that didn't fit well.
I think, like any other magnet program, it really depends on the kid how that turns out. IME IB is pretty rigidly defined, and for someone who does well with those external structures, it's a good program. For others, like two of my daughters (both visual artists, with the attendant free-flowing artistic sensibilities), it would be deadly.
