In my experience and from what I know, 'God' is always experienced as a concept, unless the person is actually mentally ill.
Now, you can have a powerful experience of a concept. I am not discounting the visceral drama of religious ecstasy, the fact of delirious visions (ascribed later to God's influence), nor the pervasive feeling of God's presence that deeply religious people apparently feel. These experiences are exactly analogous (in the order named) with intense experiences of hallucinogenic drugs, the deepest depths of fictional creation, and the general sense that 'everything's basically all right' (Taoistic order) or at least coherent (scientific order).
I can vouch for this personally, because I have been in five of these six states.
You may or may not know that as a child, I was rather religious, something which carried over until I was about 15. In my journals I speak of having 'visions', which I identified as not only divine in origin, but also artistic in intent. I too used to see God everywhere, even in the toilet bowl; and later, when I became a half-assed Taoist, I felt the same sort of mysterious immanence in the world. I have had at least five deeply moving hallucinogenic experiences, and from what I've read of religious ecstasy, it sounds a lot like a hallucinogenic experience, plus a substantial erotic component. I've never been 'saved' in this old-time-religion sense, but as luck would have it, I just finished reading a novel which is full of people having just these religious ecstasies and visions, and one suspects that the author himself had 'been there'. (The book is Go Tell it on the Mountain, by James Baldwin.)
You also may or may not know that I formally renounced religion when I was about 15. The scientific attitude is coherent, aesthetically satisfying, and terrifically dramatic. I'm not capable of formal scientific understanding (highest level of math: precalculus) but the facts of the world, and even better, the theories, just excite me. I've been reading a book about superstring theory that... But anyway.
-- written March 8, 2001