ETH is an incredibly supportive and educational place when you want to do research. I would encourage any student to do their PhD at ETH. But considering the fact that ETH is rated as one of the best schools, (or even number one in my domain) the teaching is very bad. Students are mostly expected to guess what are the requirements and to study these individually because often the lectures and the materials are incomprehensible and a chaos. It feels like the best researchers become professors even though they have no qualifications for teaching.