In my experience, it's excellent. I definitely found my IB classes a lot more intellectually challenging and invigorating than my AP classes. The curriculum is well-rounded and in-depth. Plus, the requirement of choosing only 4 HLs provides an automatic defense against excessive commitments.

I'm not sure how generalizable my experience is though. My AP classes were at a normal public high school while my IB classes were at an elite boarding school. I will say that the exams are definitely much better for the IB (they're much more detailed and require actual understanding rather than rote memorization).

I did IB. It's the best you are going to get in the US. What are your reservations?

Time demands. It sounds like the program is a lot of work and I don't think having school crowd out everything else is necessarily healthy.

I'm a slacker and I did fine in IB. She will have to work more than the average high school student (that is to say, more than basically zero) but it's completely possible to have other hobbies and activities.

That's good to hear. Thanks.