I've dated both. At the end of the day, it was not the absence of empirical measure or the limits of philosophical understanding that stood between us but, rather the purpose and end of all things. As a person who has exercised considerable effort into understanding both sides of many different arguments and perspectives, I can say that there is a deep seated labeling that occurs in order to justify one's experience. The more experience a person possesses within a school of thought, the less likely they are to be open to the possibility of alternative explanations regarding such fundamentally intrinsic tangibles as Consciousness and the perception of the passage of time. However, these differing opinions, stem from the expectations that exist based on the framework a person has derived their own background. Essentially, the foundation for propagating and creating ideas is a filter by which concepts must pass before the validation of whether or not these concepts are even admissible. Such a foundation is rooted in Morality, Permissibility and whatever initial philosophy the person is internally pandering to.
The values and differences of things like the meaning of 'equality' and the virtuous nature of ideas like 'Honor' are necessary hurdles to people actually being able to communicate the importance of their own belief structure. Also the understanding of the existence or non-existence of the soul. The value of human life, the sanctity of the human experience, the underpinnings of social constructs, politics and spirituality all make-up the filter by which our perspective is seen. In the same way that a person who hoards junk and a person who keeps nothing have different value constructs to justify their particular position, the underlying fundamental psychological mechanisms by which these formulations have been established runs far deeper than merely a price index.
To define a belief by the absence of a belief, is in fact a negative definition. Which is why a lot of Atheists tend to label themselves as humanist, strong or weak atheists. However, this does not negate the fact that having an absence of a defined belief in a God( or the absence of a defined belief in anything) does allow for a moral vacuum to form, the extent of which is immeasurable.
However, this is not to point the finger at Atheists and say, "Stalin was an atheist, therefore atheists are capable of anything!" No idea in the history of mankind has had an equal effect on everyone who has heard or believed this idea to be true. The same can be said of Christianity, however where Christianity succeeds and Atheism leaves much to be desired is the fact that Christianity has established a moral code and the structure to socially enforce the rules provided within that code, as well as the consequences for violations of said code.
Granted I'm taking liberties here but, Christianity is not limited to merely being a moral code. It is a belief in a God that supersedes the Empirically Observable Universe and has provided the navigational means by which to overcome a very tangible thing like death. If one is truly an Atheist then by definition they can make no positive claims concerning a God they do not believe in. However, as with most things, meaning supersedes the literal definition of terms and most Atheists are in fact reactionary Anti-theists governed by the need to invalidate fundamental properties of Christianity like Faith, Righteousness and the eternal Soul. Buddhists do not believe in God (or a god) yet they have not subscribed to this form proselytizing.
So to really answer the question concerning the compatibility of Christian and Atheist. Fundamentally, one or the other person would have to be divested of his or her foundational understanding of the mechanisms by which they have found purpose (or the absence of) for their existence. I am a Christian, I was an Atheist. At the end of the day it was Science, Philosophy and more importantly Grace (& Love) which made remaining abject to the existence of God, impossible for me to stomach.
.. although perhaps a 
