If you can imagine back to your comparative religion class, you will recall your teacher touching on a number of motifs shared by many a faith. Aronofsky focuses on love as a way of transcending death. Not Love of God but love between Man and Woman here on earth, which is ranked rather low by the very same religious traditions he cribs from.
Being unfaithful to the material is one mistake, the fact that he throws so much at you dramatically without any development is a cardinal foppa that sinks the film. The actors are all game, the script is a muddle, and some of the visuals are beautiful while others are painfully laughable.
If you want to know how some people can muse about the hereafter with any reference to God (which amounts to going nowhere fast) then see this.
I'm probably in the minority here, but Aronofksy's stuff has never really impressed me. Pi and Requiem both seemed like A++ student films, if that makes sense...showing a promising command of the language of film but not quite knowing what to do with it yet. Don't get me wrong, both films contain moments of genius, but they never added up to something really special.
The Fountain is the same way for me, but I think it's his worst of the three. I think I could see what he was going for--the movie sort of evoked his "vision" for me, without ever really being that vision. I thought the visuals were incredible, though--syzygy, I'm curious what you thought was laughable. Everything looked pretty damn good to me.
I'm not sold on Jackman yet...I loved him in The Prestige, but he was iffy here for me. He seems to do a lot better when he's playing someone other than himself. When he's just acting as himself, his own present-day persona, as in the scientist portion of Fountain, he seems to rush his lines and not breathe with the pace of things. But he was convincing in the rest of it. I think sometime soon he'll fall into a role that really fits him, with a director who's really in tune with him, and he'll turn in an Oscar-level performance.