You guys who expect it to be Google + Wikipedia + Mathematica + fluent in English are just setting up unreasonable expectations. If I build a new power plant and expect it to match the energy output of the sun, I'll be disappointed too.
It was designed to be first and foremost a computation engine. It's not intended to replace Wikipedia, or Google, or Mathematica. Read http://www.wolframalpha.com/about.html" for more details. Note a few things:
Goals
Wolfram|Alpha's long-term goal is to make all systematic knowledge immediately computable and accessible to everyone.
It's not intended to be a dictionary, or a math/physics text, or anything of the sort. It's meant to give you immediate access to data, and be able to offer some relevant graphs and computations with that data. It doesn't have all the worlds data in it yet (and probably never will, considering how fast data is generated), but it has a lot.
Our goal is to accept completely free-form input
I think considering that I can't even understand what some people type onto the internet, it will never be completely free form. They're going to try to get as close to that as possible. They do this much better than Wikipedia, but perhaps not as well as Google (though you don't get the proverbial digital diarrhea of websites that you do from Google). It needs some work to perfect, and I expect this to improve over time, though as long as there are people typing things online which I can't make sense of, I don't expect their algorithm to make sense of it either.
As of now, Wolfram|Alpha contains 10+ trillion of pieces of data, 50,000+ types of algorithms and models, and linguistic capabilities for 1000+ domains
This should make it abundantly clear that it's designed for retrieval and calculation of data, rather than general definitions/education.
Future
Wolfram|Alpha, as it exists today, is just the beginning. We have both short- and long-term plans to dramatically expand all aspects of Wolfram|Alpha, broadening and deepening our data, our computation, our linguistics, our presentation, and more.
This is, like Wikipedia, a never ending effort. There will always be more to add, as well as simply changing things to better reflect the expectations of the current generation of users. It's impossible to release it completely "finished", since it will
never be completely finished.
Wikipedia, Mathematica, Wolfram|Alpha, and Google are all very different. Each one excels at some things, and fails at others. You don't search Wikipedia for instructions on how to sew, you don't ask Mathematica to define terms for you, you don't ask Google to solve differential equations, and you don't ask Wolfram|Alpha for introductory calculus lessons. There is some overlap between each of them, but as long as you use each of them as they were intended, you'll be able to get the most out of all of them.