I wasn't overly impressed really. I asked 'when did the civil war start?' with the answer being returned 1861. Well, yes. If I was referring to the American Civil War - though a more precise figure would have been appreciated, but what if I'd meant the English Civil War? My next question was 'what is Meatloaf's newest album called?' It wasn't able to work with that at all. My 'what is the population of London' resulted in 11,320,900, but I don't know what the source for that was, and how current the information is. I asked (as Tara did) 'What is the square root of 12?' and got "The square root of 217 is approximately 14.730919862656." Finally, I asked a question with the @AnswersDotCom in the middle of a tweet, and that was a no hoper.
It's a great idea, but not something that I'd use yet - there's a tremendous amount of work required yet. It'll happen, there's no doubt about that, and we'll see a lot of this happening in the future as search engines use Twitter as a search interface. But the service succeeds or fails on the data it has available, and on that alone, this service doesn't cut it. However - try it out yourself - see if you get better answers than I did - you don't need to follow the service, just tweet including @AnswersDotCom in the tweet, preferably at the beginning. Alternatively, use the hashtag #answersdotcom or #hoopoe but don't hold your breath!