As mtgentry replied, Craigslist had a huge advantage in being first to market. But now as Craigslist is being supplanted by more niche focused sites, you better believe that good design will be an integral part of those new sites. Refer to http://thegongshow.tumblr.com/post/345941486/the-spawn-of-cr...
Not to mention, with apps like Padmapper, Craigslist is quickly becoming a data source with a really lame API (i.e., scraping), rather than a frontend in and of itself.
The existence and popularity of various "Craigslist overlay" sites is plenty of evidence that design and usability is important to users.
Yeah. I knew someone would call me out for saying the thing about ugly sites right after mentioning Craigslist but I think my point still stands. The only reason I felt I could safely say that was because of your point exactly, imjk. Thanks for saying it better than I could.
No, your point doesn't stand when it's predicated on imjk's skills at predicting the future and a rhetorical interpretation of Craigslist's life so far.
Both history and reality confirm for us that ugly sites other than CL do just fine.
The existence and popularity of various "Craigslist overlay" sites is plenty of evidence that design and usability is important to users.