The only reason Cuil got any attention at launch is because it has been built by some former Google employees. The wild claims about the size of the index are a joke in light of Google's 1 trillion pages announcement. Also, the site had a horrible start - search terms producing no results, the site being unavailable, etc. I think it will simply fade away quickly and be another VC money sink.
Yahoo even made fun of cuil:
Yahoo Exec Makes Yuil: Looks Like Cuil, With Better Results - washingtonpost.com