I use the DL campaign setting as my standard campaign setting (and have done for the past ten years or so). Reasons why?
1. I like the epic fantasy feel - the over-arcing plots, the good vs evil theme, the focus on character and story.
2. Ansalon (never mind the other continents) has a plethora of unexplored areas that allows me to develop my own adventures completely unrelated to the metaplots of the gaming and novel material. This makes it quite possible to run a standard dungeon crawl when my players and I are in the mood for it. I can also mess with the good vs evil thing and run a 'grey' adventure with scheming local politics. The standard setting need not restrict DMs.
3. To play devil's advocate regarding some of the previous comments in the thread, there is an advantage to the way the world has changed so much - bearing in mind the potential for time travel in DL, it means I can take my group anywhere in the history of the DL world for very different types of adventure.
There's plenty of stuff in DL I don't like too - some pretty iconic stuff - I hate DL gnomes, I'm not massively keen on kender, and I didn't like the dragon overlords (and other iconic characters) impinging so much on the metaplot. But when I run my games, I mostly ignore that stuff. I tone down my kender, I tend to use the dragon overlords as distant plot devices rather than in-your-face villains, and I blow up most gnomes before they get anywhere near an adventure of mine. I believe DL is there to be used and abused.
Those who don't like certain aspects of DL should look at the existing and upcoming product lists for DL:
Liked the old novels and original DL gaming series? A 3.5 conversion is on its way of the original series.
Don't like them? A completely new mega-adventure is 2/3 completed, mostly unrelated to the original series, several decades on. Its even got cool dungeon crawls in.
Don't like the new Chaos War/Age of Mortals thing? Pick up the War of the Lance (or upcoming Legends of the Twins) hardback and run your games back before it got 'so screwed up by WotC'. I'm expecting they'll release sourcebooks for previous ages too.
And as many people have said, there's plenty to mine for your own games outside the DL setting, too, with products covering arcane and (upcoming) divine magic, and the excellent bestiary.
/fanboy rant ;-)
But, horses for courses, nothing can appeal to all of the people all of the time (to mix my metaphors). I just believe that DL can offer excellent gaming for old school DL fans and to some of those who found the old DL not to their tastes.
Simon Collins