When we introduced new overloads of BsonDocument constructors and methods with a non-generic IDictionary parameter (which we did to be Powershell friendly) we created an ambiguity with other overloads with a generic IDictionary<string, object> parameter. Here's one example that won't compile anymore:

var dictionary = new Dictionary<string, object> {

};
var document = new BsonDocument(dictionary);

There are others that need to be found and fixed as well.