I would argue that monotheism itself is an academic descriptor used as a means of categorizing, and thus simplifying the study and comparison of religions, which is potentially problematic anyway...
Or to put it another way, the cultures from which the religious traditions we are talking about didn't sit down one day and decide "let's create a monotheistic religion!"
It's a model which any relatively intelligent person can use to describe a myriad of religions; Judaism, Christianity, Islam, Hinduism and so on, yet each of these religions (except perhaps Islam) has little knobby bits that make placement into this compartment somewhat labor-intensive.
In other words it's a hole we have created arbitrarily which we are now attempting to fit different pegs. The discussion seems to revolve around which pegs fit and which pegs don't fit.
Depending on the degree of compliance with the limitations set by the definition of monotheism, different religions fit better than others. Thus we do not have a binary "yes it fits" vs "no, it doesn't fit." Instead we find Islam fits pretty well. Judaism fits, but not quite as well as Islam. Particular sects of Christianity fit fairly well, but others do not fit AT ALL (Roman Catholicism for instance is a pretty bad fit.)
And so on...
Perhaps we should be discussing the similarities between the pegs rather than their compliance to an arbitrary hole.
Just a thought. *shrug*