cuil. a brief look
So Cuil opened up their doors.
my initial impressions is that they are doing the basic search quite well, but are pretty basic when it comes to categorization, related searches and typos. For example 'madona' doesn't even mention that you might be interested in madonna the entertainer. and there is no link to recent news about her.
Their search results seems to be the same as google's for some results, and very small for others, So I'm guessing they need a bit more work there.
Categorization also fails for something like 'PLSI' whose abbreviation means 3 different things. (a Law thing for native indians, a Learning Style, and a clustering algorithm).
so for now I'd say Cuil is interesting, but needs to beef up it's IR/NLP capabilities before it gains parity with the other engines like yahoo, aol, gigablast, and of course google.