It's so relative, it's really hard to say.
For example, I think that the extra $100 or so per night to upgrade from a value to a moderate is worth it, for the in-room coffeemaker, bigger room, queen-size beds, more attractive theming and decor, second sink, privacy screen/doors around the vanity area, and in some cases, a Murphy bed so the kids don't have to share. These are all amenities that my family uses and appreciates, daily.
However, paying up to $450-$600 per night (or more) to upgrade to deluxe, for an even bigger room, an extra toiletry or two, an onsite fitness center or childcare center or spa, onsite signature dining and super-duper theming and decor (and in some cases, more convenient transportation to one or two parks) is NOT worth it to me, since these are things that don't really impact my family's vacation experience in any significant way. They're nice to have, but not at that cost!
(That being said, we have stayed -- and would again -- in deluxe resorts, but only by renting DVC points for a studio that comes out to $250-$300 per night, which in my opinion, does give us great value for what we're spending, as it gives us most of the same deluxe standard room amenities, plus an in-room kitchenette, for little more than the cost of a non-discounted moderate.)