So far it has traded well above its NAV, but I just think that is because it has been super clunky with low volume. Hopefully volume will pick up and it will start to mirror BTC more accurately.
http://grayscale.co/bitcoin-investment-trust/
GBTC is a fairly closed system. It might explode when the pressure rises. Might produce some news articles, but otherwise a poor indicator of anything for the rest of us.