I do pay-per-click advertising and search engine optimization for a living so I'm a WEEE bit familiar with the search engines
Google was a welcome breath of fresh air a couple years ago and is still the top dog. But the competitive advantage it enjoyed is now diminishing somewhat as more and more search engines are increasingly utilizing ranking algorithms similar to Google's (i.e., rankings results based heavily on inbound link popularity.) For the vast majority of general searches this algorithm works very well as it gives you sites that are considered more authoritative in that particular area. However, once you start hammering down to more detailed searches using longer query strings, that advantage quickly evaporates into nearly nothing as they're all then fairly equal (with some actually doing better than Google at times.) In fact, one of the main reasons Google might still seem superior on these more detailed searches is due to the sheer size of their index which is considerably larger than most of their competition.
Google's still my primary search engine of choice, but I also use others quite a bit. Anybody looking for some other backups, I'd highly recommend:
-Teoma
-Alltheweb.com (aka FAST)
-Wisenut (they're still working on this one, but has done
VERY VERY well for me at times.
Here's a search engine 'report card' style article I just received a few minutes ago from one of my e-mail lists. Pretty relevant to this subject.
And from a historical standpoint, I still remember the first time I used the now dead Infoseek back in the mid-90s. I was floored, by how much better it was than all its competition at the time. Likewise, Altavista was one of the best engines going in the late 90s.