Many of the dorms were remodeled/being remodeled right now. Those ones are pretty nice: clean bathrooms, clean walls, basically clean (and new) everything. But the few that weren't remodeled are quite difficult to live in. It has also been noted that the Tercero dorms are too close to the animals and often wake up to a nasty scent of cows. Segundo area seems to be the best, as many buildings were remodeled and it is close to most classes and places to hang out in.
This really depends on the dorms that you are place in. There are two that are on campus, and the third one is off campus, but it is within walking distance. Some dorms are old and some are new. I believe they are remodeling some of the old ones right now. Many people at the beginning would worry about having to stand in lines for the restroom and showers, but that rarely to no chance of happening.
The dorms are really fun! I personally really like them. New kinds of people and you get a chance to meet them all. Usually people become really good friends with the people on their floor. Also the RA's always have events in the lounge which helps meet people as well. Sometimes we stay up late and it is so much fun. The dorm life is a must for everyone to go through at least once in their lives!
I was in one of the older dorms called Malcolm in the Segundo Dorms section. It was small and compact between my roommate and I, but it was cozy. The Malcolm building is now redone and looks a lot better than it was when I was a freshman. All the dorms here at UC Davis are beautiful and convenient. The dorms are only for freshmen though. After one year, you leave the dorms to find apartments around the city of Davis and live with your committed roommates. If you want to stay in the dorms for 4 years, there's a special request form...or you can just apply as a Resident Advisor.
As far as dorms go their are 3 main areas, Segundo, Tercero and Cuarto. You definitely want Segundo if you're into Greek life and partying. You definitely want Cuarto if you want to throw your own parties. And you definitely want Cuarto if you want to be super close to the majority of campus. Cuarto is technically off campus but it's not that bad of a commute. The dorms are dorms, and its what you make it, but the rules are a bit much and you'll be over it come winter quarter.