I'm going to keep my eye on Mike McIntyre's blog. He has started a series detailing how to best migrate your old VB 6.0 applications to VB.NET. His company has done it time after time (they are starting their forty-sixth project) and he knows the pitfalls.
Does you company need to make the jump to .NET? Check out the series.
Surprise, switching to C# is not one of his options. Stay with what your developers know and love(Visual Basic)