I would not endorse all-out consumption of something that has not been a traditional part of human diets:http://www.westonaprice.org/farming/hempandkenaf.html
If you scroll down to the part where it discusses hemp as food you will see their concerns about hemp oil. The article does not specifically address protein powder, but you may want to look for more information before you start consuming it en masse.
Hemp sounds like a miracle food but then so does soy and I no longer feel comfortable consuming many soy products. I say this having been vegetarian for 16 years until after my 1st pregnancy. That would still be my preference but to get the level of protein I want (like you) I would be tempted to consume either hemp or soy and I don't feel confident either is safe for gestating or nursing my offspring.
Your decision, of course - but I felt obligated to post the link for you since all the replies you had received so far were favorable.
It's tough finding good sources of protein! I hope you find a clear and science-based answer that you can feel comfortable with.