Some of the theories (actually most of them) are not solid; they want to find a deep meaning and a big, relevant symbolism to every detail in the film. Somehow it keeps you interested and you don't regret the 90 minutes you've spent watching it.
I bet even non-Bond fans are going to love this one. "Casino Royale" used to be my favorite, but now I guess we have a winner. The only thing this movie is missing is a strong Bond girl, but hey, I can't have everything.