buy.com secured victory, due in part to its free shipping and fast customer service responses, in the latest PowerRankings of online electronics sellers by Forrester Research, Inc. (Nasdaq: FORR). Forrester PowerRankings combines survey data from online consumers and unbiased shopping tests to provide objective rankings of the leading US eCommerce sites. The companies that rank below buy.com are Amazon.com, Best Buy, and Egghead.com.

buy.com fended off another strong showing by Amazon.com, winning a PowerRankings category for the first time. Low prices — for both products and shipping — have long been a hallmark of the site, but its speedy buying process, thorough online help, and quick-loading pages ensured its win. However, the site still has its weaknesses, such as having no real-time inventory information, express checkout, gift-wrapping, or customer reviews.

Second-place Amazon.com’s site is easy to use and brimming with features like customer reviews, gift-wrapping, and the fastest express checkout of all the sites tested. But its customer service — both email and phone — continues to be a problem. The customer service phone number is nearly impossible to find on the site, and the Forrester shopper had to wait an average of four days for email responses.

“buy.com is usually the cost champion, but this is the first time the company has ranked first overall in a PowerRankings category,” said Tom Rhinelander, senior analyst at Forrester Research. “While the shopping experience at buy.com continues to improve, its victory was no doubt aided by the deteriorating customer service at Amazon.com.”

Best Buy takes top honors in customer service because of its quick email and phone responses. But to challenge the leaders, Best Buy must eradicate site failures during product searches and add shopper-friendly features like express checkout and gift-wrapping. Business-focused Egghead.com continues to get better, but it still lacks many basic features like an online address book and product reviews.

For the latest PowerRankings, Forrester surveyed 20,000 consumers from the NPD Group’s online panel. These consumers identified the eCommerce sites that they purchased from most recently and rated their experiences. A team of Forrester shoppers then evaluated the shopping experience on sites that have a statistically valid number of consumer respondents by performing a series of rigorous tests. The consumer data and Forrester shopper scores were then synthesized and weighted, with consumer views accounting for two-thirds of the overall PowerRanking. A complete set of PowerRankings results — both consumer and Forrester shopper data — is made available to all ranked companies free of charge.

In the coming weeks, Forrester will be announcing results in additional PowerRankings categories. Additional information about each of the categories, including a complete set of rankings and scores, can be found at the PowerRankings Web site — powerrankings.forrester.com.