For the fourth consecutive year, J.D. Power and Associates has ranked Apple highest in customer satisfaction among smartphone manufacturers.

Apple scored 800 out of a possible 1,000 points, according to the J.D. Power study that asked over 6,800 smartphone owners to rank their experiences between January and June 2010. The study, released today, showed that Apple scored particularly well in ease of operation, operating system, features, and physical design.

Motorola, at 791 points, and HTC, at 781 points, grabbed the second and third spots, respectively.

The factors key to overall satisfaction among smartphone users were, in order of importance: ease of operation (26 percent); operating system (24 percent); physical design (23 percent); features (19 percent); and battery function (8 percent).

With the popularity of the App Store, it should come as no surprise that mobile apps are becoming more important to smartphone users. More than two-thirds of users download games and 54 percent report downloading travel software like maps and weather applications. The study also showed that 41 percent of smartphone owners download utility applications and 36 percent download business-specific apps.

J.D. Power also released a study today on customer satisfaction with traditional wireless handsets. That survey found that owners of traditional mobile phones are keeping them longer. J.D. Power pointed to the economic downturn as one possible reason for that.

Earlier this week the University of Michigan's American Customer Satisfaction Index ranked Apple No. 1 in customer satisfaction for the seventh straight year.