I'm looking more toward CMSes as I'd like my clients to be able to be as self sufficient as possible. Anyhow, I'm just starting to evaluate and will update this with my conclusions. However, since I'm starting with evaluating Umbraco first, I'd like to get a consensus.
I have no preference for C# or VB.NET. so I'm open to either.
Umbraco CMS is a very flexible CMS. The core code of the product is written in C# but really you should never have to read into the source of Umbraco as its so eay to extend.
You can use .NET masterpages in V4 of Umbraco along with .NET usercontrols written in VB or C# which ever you prefer.
I recommend you take a look and let me know what you think.
Here are some links to get you started.