Hi there. PBL is a fairly big part our curriculum, occupying 2 to 4 hours of actual PBL time (depending on the particular Block) and an additional 2 to 6 hours depending on how much time you need/decide to spend preparing your learning issue (a somewhat detailed answer to a medically relevant question related to the PBL case for that week that each student will research on his/her own by going on PubMed, AccessMedicine, etc.).
As to how worthwhile it is, the purpose of PBL at UCLA is quite logical: there is way too much medical knowledge (which is constantly being updated/added to) for any one physician to know, so they want to teach us where and how to find appropriate resources/knowledge with which to take care of our future patients, and I think PBL is very worthwhile in this regard. It is also designed to give you some experience with differential diagnosis and selection of appropriate diagnostic tests, etc. Personally, I love trying to figure out what is wrong with the patient in the case, what tests we should order, etc. Also, PBL is a great opportunity to get to better know many of your classmates (which unfortunately is difficult to do in lecture with a class of 150 or so students). On the other hand, however, I'm not a big fan of writing so I find myself spending a fair amount of time trying to write up a good learning issue that flows logically and makes sense. Learning issues are for your PBL mates (usually 8 or so in each PBL) to learn from, so I take it kind of seriously and put in some effort. Other people don't as much, and that's fine too.
Regarding redundancy, I'm a first year so I've only gone through some of the stuff one time through. But it is my understanding that we have a second (and more in depth) round of most of the subjects we covered in the first year during the second year, such that there is a cardiac, renal and respiratory physiology 1 block (usually 9 or so weeks) in the first year and cardiac, renal and respiratory physiology 2 in the second year. Honestly, I really didn't worry about things like this too much. You will get an excellent medical education at UCLA no matter what, and this is largely the reason I decided to matriculate here. I hope that helps.
School is starting again on Monday, and they keep us pretty busy, but I'll try to check this thread from time to time in case anyone has any more question that I can answer. In the meantime, congrats to those who've been accepted and best of luck to all of you who are still waiting. I was in your shoes last year and know how difficult the waiting game is, but it'll be over soon enough and it will hopefully result in your matriculating at your top choice.