I've been rereading The Living Greyhawk Gazetteer lately. I have to say, using this book with a few of the Moore era supplements (Giants and Scarlet Brotherhood) is easily the best version of the setting. I know that will piss off the grognards, but I find just tons of cool things in these books, many of them geared right at players.
I do think the 1e box set was ok for its time, but the books were largely just lists of numbers and a paragraph or two of information for each entry. It provided a nice springboard for do-it-yourselfers that didn't want to make a completely original world, too. But compared to the later stuff, it's kind of dull.
Things I really like in Moore/Living Greyhawk:
1. The split of the Great Kingdom into multiple, antagonistic entities (and seriously, the Great Kingdom? That's the best name Gary could come up with?).
2. The Scarlet Brotherhood is exposed. It's still tough, but has suffered some setbacks.
3. Iuz is more powerful, as a demigod should be. But even he is facing rebellions.
4. Plot hooks everywhere. Seriously. Every kingdom has a list of current issues that any PC group can tackle.
5. I have the 4 poster maps published in Dragon, and they show all the published module locations, which is awesome. And those maps combined blow away the Darlene map.
6. Pictures of each race, which while seemingly minor, is very important for showing players and giving them a very quick idea of what each race is about.
7. Mayaheine. I like the Joan of Arc-style demigoddess.
Stuff I think it missed out on:
1. Busting up the Circle of Eight. This felt contrived to me. The newer members are nothing special, either.
2. The adventures actually published (Doomgrinder, etc), were underwhelming, except for the Giants redo, which was half sourcebook and very well done.
3. I LIKED Ivid as a bad guy. Trapping him in Rel Astra (and basically removing that city from the world for most campaigns) just sucks.