I've been using Vatlab's FVK for a year now, and it's hands down a must have in your arsenal of tools for Facebook application development. The C# SDK's for Facebook are good, but they don't come close to the resources provided in the FVK.
No other SDK provides the amount of controls, usage & real-world examples of how to use the code, or actual "working" source code that the Vatlab FVK does. Plus, for the money, the amount of savings on development costs incurred by having
this toolkit are astronomical! ...Not the mention the support, which makes or breaks a software's success. The support I've gotten from Vatlab is stellar.
I was able to perform publishing operations using Vatlab's Stream Publish Pop-up control that would have taken literally hours to do. Also, using these controls helps keep your code clean and efficient! I can't speak highly enough of this toolkit
and look forward to future releases!