I think it depends on major. Obviously, any weeder class that is a pre-req will be super-hard because its purpose is to weed applicants out. And, of course, one can assume STEM will be tougher. My daughter is in Media Studies at Berkeley (granted a less-tough major). She says her CCC prepared her well. A bit more reading and general studying, and more papers, and things go faster. Each class starts a new topic - there isn’t a kind of rehash that a CCC might have week to week. But she is remaining mostly comparable to her CCC grades - about a minus sign difference. It’s still early in the game, of course.
They have a student learning center with essay and research workshops, which have given her a lot of pointers. And she says, thus far, all her GSIs (TAs on other campuses) have all been super-supportive, saying their jobs are to aid the student in doing the best he or she can. They aren’t tough or mean. I don’t know if this is a campus-wide mandate or she just got lucky.