This is possibly the most ambitious site I have created. The site owner estimates that once he has finished uploading his stock, there will be upwards of 10,000 books on the site. Obviously this had ramifications for the way I developed the site, and for the server once it was live!
This allowed me to explore the Couch CMS cache function, something I hadn't really used before (mainly because I hadn't built a site on this scale before). After a few initial teething problems, it worked like a charm. The authors page, which previously took 20+ seconds to load the 1000+ authors, loaded in a couple of seconds. This is just one of reasons I love Couch CMS so much, as I'll probably tell you when I'm convincing you to get your site made by Sprucemoose!
Aesthetically the site is fairly basic - this is the look the client wanted, the books are the focus, not the site. The real power of the site is in the back end, the afore-mentioned caching system, and the advanced search options that let you search anything you want.