Downtown Disney used to warrant at least a couple of visits during our relatively short trips to WDW which were just under a week. Always loved to hit the World of Disney and Xmas shops. There were few other shops we liked to check out as well. We used an evening trip to DtD like other folks use a mid-day break to relax, shop a bit, have a nice meal somewhere and Ghiradelli's for dessert.
As a quick-service, restaurant, dessert or night-life destination - it's even better now.
With DS, it's as if the more buildings they add the less I like going there. It used to have a nice layout that was simple to walk around and see everything, but now I can get lost there with the buildings seemingly taller and all the added side streets and walkways. And of course, some old favorites are no longer there - Fulton's for one. And it's more crowded now - I'm not sure if it's because some open space was used for more shops, or it's just that much more a draw now. With all this combined, I find it that it's not as relaxing an experience as in the past.
Now we only plan going to DS on travel days where we weren't planning to hit any parks. I can't see sacrificing park time going there unless I had a specific ADR or was meeting someone who happened to be in the area but was not going to WDW. It's still a must go-to place, but we just don't spend nearly as much time there anymore.