I have visited almost all the UC's (I haven't seen UCSF or UC Merced). I've known many friends and family members who have gone to them as well. So not only did I get to see the campus, but I got to see the dorms, sit in the libraries, attend lectures, eat in the cafeterias, etc. I also have a sister that is attending UC San Diego right now, so I have visited her on many occasions.
My parents were very proactive in touring colleges. I have researched most of them and have seen them in person as well. I'm not the best source, but I'm a student's eyes. What were first impressions? I'm not biased in any shape or form so this will hopefully bring light to any grey areas.