Christians and Muslims: Worshipping the Same God?

Philosopher Bill Vallicella has an interesting post on the question of whether Christians and Muslims worship the same God.  His post is entitled The Debate That Won't Go Away: Do Christians and Muslims Worship the Same God?  He summarizes in this way:

Most of the writing on this topic is exasperatingly superficial and uninformed, even that by theologians.  Fr. O'Brien is a case in point.  He thinks the question easily resolved: you simply note the radical difference in the Christian and Muslim God-conceptions and your work is done.  Others make the opposite mistake.  They think that, of course, Christians and Muslims worship the same God either by making Tuggy's mistake above or by thinking that the considerable overlap in the two conceptions settles the issue.

My thesis is not that the one side is right or that the other side is right.  My thesis is that the question is a very difficult one that entangles us in controversial inquiries in the philosophies or mind and language.  

You might say it doesn't matter.  If Christians and Muslims worship the same God, then Muslims are heretics: they have false beliefs about the true God.  If Christians and Muslims worship different Gods, then the Muslims are idolaters: they worship a nonexistent god.  Not good either way.  This won't be acceptable to Muslims, of course, but why shouldn't a Christian say this and leave it at that?