What if God did exist?

I never used to like Twitter, but the people I follow on there sometimes come up with some neat stuff that makes me think, in many different ways. In this particular case, I was goofing around with the #IfGodWasReal hashtag, and headlessBortok expressed some incredulity at my line of reasoning. As an aside, I'm fine with that; Bortok's a reasonable, inoffensive guy. But the brief conversation we had made my mind swing onto a path it had been skirting in the few hours since I tweeted that tweet. The question, quite obviously, is largely meaningless to theists, but I pose it to other atheists:

What if God actually did exist? How would the world be different? The potential for answers to this question, at least as far as my speculation goes, is enormous. You can range from enormous implications (We'd all be of one religion, because there'd be actual evidence) to tiny ones (Churches would have better attendance). Or anywhere in between. Or bigger. Or smaller.

The potential here is quite literally unlimited, at least to me. Once you allow an omnipotent being into the picture, violating natural law as he pleases, what isn't possible? He could intervene at any point in time, and do or change anything. The would might be exactly as it is now - which is what theists will, quite naturally, argue - or it could be absolutely anything else.

It's a neat thought exercise. Does anyone have any ideas? How would the world be different if God existed? Let's also assume that he's far more willing to reveal himself than current theists believe him to be. He intervenes; how often? To what degree? What does he change? How does it change our lives?