Since we are using the 1.9 driver we started noticing the following exception popup (11 occurrences). We have 2 occurrences of this happening with 1.8 but it seems to be happening a ton more with 1.9. I'm sorry I don't have a repro but I believe it had to do with passing hundreds of excludes into a not in condition (which we have fixed). But I figured I'd submit a bug for it just to bring it to your attention:

System.IO.EndOfStreamException: Attempted to read past the end of the stream.
at MongoDB.Bson.IO.ByteBufferFactory.LoadFrom(Stream stream)
at MongoDB.Driver.Internal.MongoConnection.ReceiveMessage[TDocument](BsonBinaryReaderSettings readerSettings, IBsonSerializer serializer, IBsonSerializationOptions serializationOptions)
at MongoDB.Driver.Operations.CommandOperation`1.Execute(MongoConnection connection)
at MongoDB.Driver.MongoCollection.RunCommandAs[TCommandResult](IMongoCommand command, IBsonSerializer resultSerializer, IBsonSerializationOptions resultSerializationOptions)
at MongoDB.Driver.MongoCollection.RunCommandAs[TCommandResult](IMongoCommand command)
at MongoDB.Driver.MongoCollection.Count(CountArgs args)