My curiosity to know if there are any websites or UX firms that examines different websites for usability metrics led to a few fairly interesting companies, individual blogs and websites. One of my favorite studies conducted by Usography is this UX audit.
Usography reviewed 100 top retail web sites and presented their findings in "Retailer UX Audit". The sites were rated according to a list of 30 user experience feature criteria (listed in the article). The founder of Usography, Paul Bryan, summarized their findings in this article on UXbooth.com. It is interesting to note that on a scale of 30 two companies were were tied for first position. What is more interesting is the fact that these two companies implemented 16 out of the 30 features. I'm sure the article would be even more fascinating to people who worked on the 'Individual Class Project 3' (Socialite) or participated in an in-class activity where we discussed about ideas for a shopping application with social features. Aren't you thrilled to see that some of the best features that were found to be missing from many sites were actually discussed during the in-class activity? For example we discussed about features related to price comparison and visual try-ons. Though companies like Buy.com and Amazon.com which are online-only retailers take the top spots, they only implement half of the features used as the evaluation criteria. This tells us that even in case of mature companies there is a significant potential for UX improvement. I do not believe that implementing all 30 features would increase the sites overall usability. Also a thorough cost-benefit analysis should precede the decision to support implementation of any of the listed features. However this audit provides tremendous value to the companies by pointing-out areas of improvement, without the companies having to invest in a UX evaluation.
Note: Do check-out Usography's website and services. They have an interesting business model and offer several design services with a lot of focus on evaluation.