ByteStream is the foundation of our network system, and a few other systems. It's used to basically read and write raw data to byte memory, to send and receive over the network.
I noticed that in a few places we had started using a pooled MemoryStream because ByteStream was apparently too slow. This hurt my feelings because I made ByteStream to be a faster, zero allocation alternative to MemoryStream and BinaryWriter/Reader.
So I spent some time speeding it up. It's now on average 5x to 50x faster than it was.