In past years we have stayed at a number of rental properties in OC and Fenwick and we certainly always enjoyed it! That said, there are a few considerations with respect to location and design that can greatly improve your experience.
1. Location - North OC is not downtown. It is much quieter and far more spacious but still completely walk-able. And of course downtown OC is an easy drive or bike or bus ride away when you want to visit the boardwalk.
2. Structure - Traffic noise can wear you down a bit on vacation, especially when you're staying along Coastal Highway. Atlantis is set way back from the highway; actually just a few feet behind the sand dunes. Plus it is made almost completely of concrete - thick concrete! Even the walls between the units are concrete, which means you hear the ocean, not the cars or the neighbors. It is a huge plus, in our experience.