You're right. You can mix languages but that only works with the paid version of Vis. Studio.
If you download the free Express edition you cannot mix languages.
I don't want to start a language war, but I think we should minimize the number of used languages.
The ocx will always be in C++ and I prefer to write all other code in C#.
Most new developers know C# better than VB.NET and the learning curve from java to C# is also much less steeper than from java to VB.NET.
Sticking with VB.NET for new code (and most code for v4.9 will be new) is not very future robust.