The first year is great - everyone welcomes you, takes care of you, and makes you think its a great university - then they abandon you. you're left to a bureaucratic mess and getting help is a struggle. Drop-in adviser hours are a joke - you have to shove people out of the way as soon as it opens to get a spot. Meetings with your major adviser take 1 month + to get. They claim you have meetings with advisers regularly and get help, but I've never been offered any help or "check ups". The biology major is totally confusing, as good luck getting someone to help you out.
I'm a bright, determined student and even I can't graduate in four years. First, you can't get classes. You have to show up to every section of the lower division courses and try to fight your way in. Good luck even getting on the wait list for some upper divs. If you could get into every class, you might be able to graduate in four, but don't count on it. Second, the quarter goes by so fast that even if you just miss a week of school for the flu you can get so far behind that you have to retake the quarter. Using office hours to catch up is impossible - usually a professor has two hours of office time for 300+ students, so there's really no time for one on one interaction.
If you ever get into academic trouble (I missed a quarter from being sick) all you get is threatening letters demanding you see an adviser, but by the the third week of the quarter they have literally no appointments left, so you have to battle it out in the rush on the biosci advising office. After trying to get in so many times, I finally pushed people out of the way, rushed to the front desk, and filled out the "before we meet with you" form with brief nonsense. I managed to get in that time.
When you visit UC Davis they show you the first year dorms, brag about their student services, and are friendlier than the people at Disneyland. And sure first year goes great but then they just forget about you. They don't even have adequate student housing, so you have to rent in Davis where there's no renter protection besides the overflowing small claims court. It becomes a commuter school after first year. On campus apartments are ridiculously expensive and impossible to get into. You have to be married, have a kid, or know someone who's in already and sublet from them.
Basically, you're on your own. You have to fight for every ounce of attention you get. The university just doesn't care about you, and wouldn't have time to deal with you if they wanted to. The people that work there are friendly but have no substance - the majority will just smile at you and then not help you.
If this was the end of my first year, this would be a glowing review. But by now I'm sick of the smiley staff and how determined they are at being unhelpful. I'm tired of having to cover rent for a roommate who won't pay because most apartments only take one rent check. I'm tired of dealing with security issues with my roommate's crazy boyfriend because the campus offers no student housing. I'm angry at how behind I got after one quarter and how now one can be bothered to help me. I'm sick of lectures with 300+ people that move so fast there's no room to breath or be interested in the material.
And I'm sick of biking in Davis! It's either raining sideways or 100 degrees out. Bike-town my bum. So basically, if you don't mind spending five years in school, never get sick, never have an issue, and don't ever need or want advising, go for it. If you're a normal human, pay for a private school. By the time you graduate at UC Davis, you will have paid enough for a small private school with a modest scholarship or financial aid.