After long ago abandoning Alta Vista for Google, I've recently found myself compelled to return, for one simple reason; Google try too hard to tell me what I'm looking for.
What I mean is this, Google are not content to let me tell them what I want to find. Their search algorithms now completely discount my use of quotation marks to group words, or to try to indicate that I really want whatever unlikely word I enter. Many of the old tricks for hinting to the search engine that you mean what you say are now ignored entirely. On Alta Vista, powered by Yahoo! (and therefore by Bing, I guess) those tricks still work.
When I perform technical term searches, which is much of what I do, I don't need the search engine second guessing my spelling. If Google would let me override their "corrections" I would continue to use them.