I’ve heard it’s very intense – they have to send out emails to people at the end of each semester reminding them that they do, in fact, need to eat an sleep, etc.
A friend went to Cal Tech and didn’t enjoy her time there, but I think part of it was because she was a girl (astrophysics major) and had varied interests, and there really weren’t many people on campus who shared her breadth of interests, few girls she could befriend (her major was very boy heavy) and few classes outside the technical areas that she could take to satisfy her curiosity. She wanted to go to MIT and got accepted there, but tuition was too high. I think for someone with very narrow or almost exclusively technical interests Cal Tech could be really good.
If your son has broader interests then MIT would be better – they really do have strong programs not just in technical fields, but in some of the humanities as well, meaning he could have some enrichment classes as well.
Stanford is fabulous and has a lot to offer of course, and it definitely puts people in a good position for success simply for networking reasons. I think this is actually a HUGE thing to consider with schools – if your son wants to do something like becoming an entrepreneur, Purdue may be just as strong technically but his network of colleagues won’t wind up being as plugged in, and so he’ll have fewer elite connections. That’s what I’ve found with going to a state school in both a highly ranked liberal arts program and a highly ranked engineering program. I had lots of really smart, talented friends, but they consistently aimed their sights lower than those people I knew who were similarly talented but went to more elite institutions.