Blekko is soon opening its new search engine, and getting some good coverage. Microsoft's Bing is spending hundreds of millions (billions?) trying to dog chase Google in search. Countless companies tried competing in search before - Cuil, Wolfram Alpha, etc.
It would be fantastic for the internet to have a real #2 player in this space, but unfortunately I'm afraid none of these efforts will be a real contender to Google in the long run, and not because they fall short on product quality. In fact, most of these products (and Bing is the best example) offer a far superior experience to Google's in many ways.
But search is a strange category to compete in. I think it has a special dynamic to it -- sort of a weird variation on the "Innovator's Dilemma" -- that makes it so tricky to take any meaningful market share from Google...
The Search Innovator's Dilemma
The trouble is that search companies (and reviewers) evaluate new search engines based on what they do well. Bing does travel search great (as well as images, and many other categories), Wolfram does data-intensive search great, Blekko apparently does vertical search great, etc, etc. It's common wisdom to focus on the things you do well, and do them better than anyone else in the world. But what works well for mostly any other category of company in the world is, I think, precisely the achilles heel of all non-Google search engines.
Because users, subconsciously, place less value on the queries a search engine handles exceptionally well, than they do on queries the search engine doesn't. In other words - a great search result for a travel query on Bing will matter less to users than getting no good results on a query for say "italian vespa collection poster" (compare to Google...)
Google might lose in the areas where its competition shines, but it doesn't matter. Our habits as users don't form there... they form on those multiple-keyword, 1-off, "non-important" queries, and that's where Google absolutely kills its competition.
Hence the 'Search Innovator's Dilemma'... to win search market share from Google, it hardly matters to one-up Google on quality, or UI, in any specific type of search. The search habits don't form there. Where you'd need to focus is on consistently delivering OK results on all those billions of queries that "don't matter", and that's a task that, it seems, is nearly impossible for a company to take on.