For us, the convenience of staying on site is worth the price (although as Disney keeps pushing up the rack rate, we may rethink that). As for the other things, well there is some magic in being surrounded by Disney -- but I think that doesn't happen at all the hotels. At Saratoga Springs, for example, there isn't much theming to speak of and it is easy to see plenty of downtown Orlando from most everywhere on property, which takes away from the immersive aspect of staying on site. We like the Epcot area resorts, which provide a lot of beautiful theming, a lot of convenience and very much an immersive resort area where the magic of a world apart can be maintained somewhat.
As for bus transportation, we always rent a car as we think the buses are miserable with noisy, awful kids and their even noisier and more awful parents. Our nightmare would be starting a vacation with "Magical" Express.
We don't bother with the dining plan as we like to go over to Universal and enjoy restaurants there such as Bice and Emeril's. The
DDP would just make us unwilling captives of Disney. Thus, DDP is not an advantage to staying on property for us.
Being able to charge things to one's room is just using one credit card instead of another. No big deal there.
And, extra magic hours have lost any appeal for us now that Disney does not hand out wristbands and lets everybody stay in the parks to shop and eat. Definitely not worth the bother. Years ago, there was something called "E-Ride Night". It was only for Disney hotel guests, and it required an additional ticket purchase. Now, that was a fun evening. EMH does not begin to compare.