Nathan,
Well, my 'biggie', if you will (in the context of VBA to .NET), would be you have, at the very least, a readability of the following:
C/C++/Java and of course C#, in relation to your question and at the end of the day, VB is VB is VB...that's it.
Couple this with the fact that C# is a brand new (and often quoted as the premier MS .NET) language and it's a win win situation IMHO.
Not to mention the fact, that .NET 'features' have historically, to this date, been implemented in C# before VB...remember operator overloading. Admittedly, some of these are syntactic shortcuts, but the point is valid I think.
Cheers,
Glenn.