1. Anyone using C#?
Syntactically it's more pleasant than vb.net and c++/cli. It also has some features like partial classes that the others does not have (yet).
2. Why is it better than another .NET languages?
I used java before, and I liked it. I find little use for it today though.
3. How do you think about Java and Ruby?
C# and .NET in general is excellent for RAD (rapid application development), quickly setting up a functional application.
4. Is it better for small project?
I found C# easy to learn having earlier experience with C/C++/Java. It all depends on you. If you come from the world of VB perhaps VB.NET is the way to start. Possibly moving to C# later when you get the hang of .NET.
5. How about the learning cost?