There are a lot of older homes in Turtle Rock from the 60s and 70s, but what gives Turtle Rock its appeal from a buyer's perspective are a few things:
1) Location: South of the 405, the cream of the crop when it comes to the San Joaquin Hills. Close to the ocean, the weather really is better in this area than say in Woodbridge or PS because you get an actual ocean breeze, while people north of the 405 get freeway particles. Also the schools in this area are the best in Irvine (if you're into that kind of thing).
2) Space: Just look at Turtle Rock as you drive around the neighborhood. Lots of large green belt spaces, wide roads, lots of parking. It was one of the original five neighborhoods in Irvine, so it wasn't over built like some poor imitation of Kowloon District in Hong Kong. That's one of my biggest gripes against the communities in the slums north of the 405. Too much density.
3) Stability: Turtle Rock has been a high end neighborhood for over 30 years. People who live in this area are generally well off in their careers, and many bought before the bubble, so there aren't as many distressed properties here compared to Woodbury or other bubble knife-catch neighborhoods that were built in the last 10 years. Couple that with a lack of available inventory (maybe around 40 homes month to month), and you get a fairly price resilient area. Just read some of the stories online about people who live in Woodbury and the type of things they put up with (teenagers racing their Civic SI's down the street, people using their condos as asian prostitution lairs, etc). A lot of pretenders faking it until they make it in Woodbury, not-so-much in TR.