In many ways, my approach to GH reflects the reasons behind my initial interest in it back in the day. I liked the setting because there was no metaplot, no novels, and little canon. If I ever use the Greyhawk wars, as an example, I'd rather use the war as a current plot point/developing event for my campaign, rather than read about it.
That's what I did in my campaign. My original campaign (which I was a player in) ran from 576-582 CY and covered the beginning of the war.
The next campaign, which I DMed, ran from 576 and is still ongoing in one form or another. It's about 594 CY now. In that time, I've dealt with Vecna, Iuz, the Greyhawk Wars - which take place quite differently in my campaign - the Age of Worms and a bunch of other stuff. It's quite a rich world now. I was able to incorporate all the stuff from the original campaign and the Greyhawk Wars and use it to drive the action and make things fun for my players.
However, I really don't like the Greyhawk Wars much. To a large extent, the Greyhawk I'm DMing today (using what's released of Castle Zagyg!) is still based on that 1983 boxed set. A few things that are cool have happened (like the Shield Lands have been overrun, and that's a major point in the campaign), but mostly it's 1983 standard.
And I'd be quite happy if the 4e Greyhawk just worked on that idea.