No, the engine hasn’t launched yet but the blog has and should be a great clearinghouse for information pre- and post-launch.
From the link:
Our teams are working hard to meet our goal of having Wolfram|Alpha ready for you in just a few weeks.
Since Stephen Wolfram’s initial announcement, we’ve had the opportunity to show Wolfram|Alpha to some of the thousands of you who contacted us. Many interesting questions surfaced. We plan to use this blog to address those questions and the many more we expect you’ll have as you think about how you too can use Wolfram|Alpha.
David Kirkpatrick 
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