Tower Records — with its excellent checkout process that includes an easy-to-find privacy policy and optional registration — leapfrogs the competition in the latest PowerRankings of online music 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 Tower Records are Amazon.com, barnesandnoble.com, and CDnow.

Tower Records finishes No. 1 in a tight race, after a last-place finish in the previous spring’s Music PowerRankings. In addition to its above-average checkout process, clear inventory information and quick phone responses helped drive Tower Records to the top. But its slim lead could evaporate if it can’t fix problems like erratic email response times and its lack of shopper-friendly features like customer reviews.

Amazon comes in second, despite high scores in many categories, due to poor customer service marks that were a result of slow phone and email responses. But the site continues to offer the most features like the ability to ship to multiple addresses in one order and the inclusion of both a wish list and gift finder.

“Once again, Amazon.com battled a tough challenger and came up just a little bit short,” said Tom Rhinelander, senior analyst at Forrester Research. “The redesigned Tower Records site provides a slightly better shopping experience — no doubt aided by Amazon’s slow customer service responses and the company’s decision to bury its support phone number and privacy policy.”

barnesandnoble.com claims the top spot in customer service with quick email responses and a privacy policy link on every page. And with a few tweaks like making navigation consistent and letting shoppers cancel unshipped orders online, the site could challenge for the lead.

Although CDnow came in last, it was just a few points behind the leaders. The site includes a gift finder and clear notes on product availability, and it displays breaking news. However, drawbacks include a lack of customer reviews and requiring authorization for returns.

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 announce the results of additional PowerRankings categories. Additional information about each of the categories, including a complete set of rankings and scores, can be found can be found at the PowerRankings Web site — powerrankings.forrester.com.