Lectures → Professors
Discussions → TAs, or GSIs in the Cal parlance
Office Hours → Combo of Professors + GSIs
Exams → Combo of Professors + GSIs
S22 has had two great professors so far - the CS 61 series has been amazing from his perspective. He has also had a couple of OKish ones - in one instance there was a last minute Professor switch (Math) and in another instance the professor was teaching course material far removed from his research interests (ML prof teaching an engineering econ class).
In general, at least with STEM students, most don’t go to the lectures at all. They watch the recorded sessions, review the notes and slides and then really dive into the material with the GSIs in a small group setting. That is where most of the real learning happens.
In other classes (like EECS 16A), the labs are absolutely critical. For one lab, S22 had to build a touch screen device from scratch using first principles of capacitance and linear algebra. Hands-on labs such as these and the difficulty level of the related problem sets have really elevated his quality of learning.