I think it really depends on where you differ. Islam and Christianity aren't really that different, so I imagine that it's possible you would find a lot of agreement on the most important parts.

But I also know that monotheism tends to be dogmatic and evangelical. It's a lot harder for competing monotheists to have a relationship than competing polytheists, because they tend to see "true" and "false" gods and religions that polytheistic systems don't normally have. I see that tear even Christian relationships apart when they're different denominations, like Baptist and Catholic. So I think it really depends on the religions and the individuals adhering to them.