Getting started with speech recognition programming questions

So, you've all probably seen Iron Man where Tony interacts with an AI system called Jarvis. Demo clip here (Sorry it's a commercial).

I'm very familiar with C#, C++ and Visual Basic, but I am unsure what options I have available for me to program something like this. Ideally, I'd like to have it assist me while working on some projects by automating a few things.

After doing a bit of research, I saw that a lot of people where using apple script. Well, I'm a windows developer and I work on windows, SO, that won't work.

Microsoft has a Speech SDK, but I hear that I can't program it to learn custom words... as in it just uses it's standard library. Is this true? What are the other limitations of speech recognition with the SDK? Is there something else then?

Also, which language would be better to use for a project like this? C# or VB?

The .NET 3.0 System.Speech.Recognition namespace has very elegant .NET wrapper classes around the SAPI SDK. Including the Grammar class to customize the recognition. As usual, any .NET enabled language can take advantage of it, the specific language doesn't matter.