I agree, however, this is one area I feel the BA list needs help. Is it still legal to ally with grey knights in tournements? From what I have read, IG/SM/SoB were the only armies that could officially have allies for sanctioned event...For tournament play in a marine army I think a Librarian is near-essential. Chaplains are very good for leading death company and potentially useful if you like to have 700 points of terminators, chaplain and vehicle in one place - which isn't for me.
I find fury of the ancients hugely useful. I like the psychic hood and force weapon too. I play my marines pretty shooty, so a chaplain doesn't make a lot of sense for me.