WP8 and new protocol

Now you can use base API.AI Library in your Windows Phone 8 project. The API is quite similar to the generic .NET SDK, but uses async methods

async Task<AIResponse> TextRequestAsync(string text)
async Task<AIResponse> TextRequestAsync(AIRequest request)
async Task<AIResponse> VoiceRequestAsync(Stream voiceStream)

Also, please note the protocol change.
Now Fulfillment field from API.AI console becomes composite field in the protocol. Earlier it was simple string field named "speech".
So, "speech" field now in the Fulfillment object. And you should change

response.Result.Speech

to

response.Result.Fulfillment.Speech

New release already in Nuget