I agree...Gandalf was tired from exerting his powers, and then the Balrog's whip was pulling him down. I WOULD like to think, however, that he sacrificed himself--partly that, and partly because of the whip. I also think that it really added suspense to the book...when we all think Gandalf's dead, and then he comes back and everyone thinks he's Saruman!

sacrifice is a misleading term in this case i would think, because, in my oppinion, gandalf did not have much choice in falling or not. I personally think that the "resurction" of gandalf was/is largely biblical in nature, gandalf being sent back to finish his task is similar to why jesus came back/stayed on earth following the resurection I would be interested to know what other peoples think about this though