While I consider myself Christian, I have an awfully difficult time with the idea of "God". Before reading Spong's Jesus for the Non-Religious the idea of God was just one of those very troubling ideas that I couldn't wrap my mind around, so I didn't. It's actually remarkably easy to just put the idea of God aside and realise that definitions aren't all that important. It's easy, but it isn't really satisfying. The question, and the fact that you don't have an answer comes up - both when you are faced with people who actively reject the idea of a God or Gods, and when you are faced with the more religious types and their questions about "do you believe in a personal God?" Actually that isn't the hardest question - it doesn't mean that you have to be able to define God. Still, the lack of a God language was problematic - I wasn't comfortable with the God language (or God ideas) that I had been given my the church, but I had no alternative. Which is one reason why I love Spong's book.
The "theistic" understanding of God as a being, external to the world, which intrudes from time to time (or doesn't, I suppose, for a deist who uses theistic language). The "Spongian" understanding of God - that you reject the supernatural, external characterisation of God - is terribly useful to me. And while it doesn't leave me with an answer to the "what is God" question, it leaves me with a set of skills that may be useful for me to formulate my own definitions. It's also nice that these definitions or understandings are just my own conception...they don't represent any sort of an objective "truth". And I find that idea remarkably comforting.