My family moved to Westlake a couple years ago, and some of my extended family a few years prior to that. Having come from Santa Clarita (about 35 minutes northeast) this was a major improvement in living quality. The only two downers about the area are the expense and the sometimes snobby people. The first problem is an inevitability of living near LA and avoiding the inland empire. The second is also an inevitability of just living in California. People in California are just slightly aloof and snobby. If money is added to their bank account then both of those factors grow as well. Sorry for the generalizations, but they are true.
Other than that the town is great. Depending on if you are on the floor of the valley or in the hills, it can be decently walkable or bikeable. Everyone is very active, which encourages you to be active. People are quite often very friendly. The shopping is great, and if you need anything that isn't in town you are 10-40 from anything LA has to offer. Malibu beach is just 20 minutes down Malibu canyon road.
No Idea how the weather got anything but an A+. In the summer it can get up to the 90's (S. California is a desert), but the evening breeze coming over the hills from the oceans rarely leaves with a less than pleasant night. Winter is mild, and spring and fall just blend into the other two seasons. It's a great combination of near beach weather without the traffic and fog of beach cities.
The schools seem to be all impeccable, even if they are filled with snooty children who get themselves into trouble with their parent's money. If you are at all a good parent, this would definitely be a lesser evil to most.
This is a wonderful place for older couples, families, or even young professionals to live and be comfortable. Like a little isolated haven away from the chaos on the other side of the hills.