I used the Classical model to homeschool my very average stepdaughter up through high school and she really thrived; however, it hasn't worked at all for my very advanced 7 year old daughter. I am guessing it might work for some gifted kids, and it is more challenging than your typical public school style curriculum, but I think it would need to be heavily altered for most HG students.
The copywork and memory work were especially despised,as well as the violence that one encounters studying world history, even at the first-grade level. I think sensitive kids would probably benefit from waiting a few more years before addressing certain historical events and violent myths that seem to be standard in Classical curriculum.
I still like some elements of the method, but it's not something I would suggest for a gifted kid in general, as it feels very prescribed and repetitive, whereas novelty and interest-driven learning seems more meaningful for a gifted student.
