I don't think Disney Digital Copies were upgrading from SD to HD prior to DisneyMoviesAnywhere. Other studios may have, but Disney wasn't.
As for other benefits of DMA, I think a big one is that prior to DMA, you had to choose which service you wanted to redeem your Disney movies with. For me, that's iTunes, but you could also choose Vudu, Amazon, Google and others. But you were limited to just one service.
With DMA, you get to choose iTunes/Vudu/Amazon/Google in addition to DMA. Here's the kicker, DMA includes iTunes, so you can redeem Disney movies with DMA, iTunes, and one of the other three (Vudu/Amazon/Google).
This is great for folks with multiple ecosystems.
Can you straight out buy Disney Movies off DMA ? and then get your Itunes/Amazon copy too ?
If so are they mostly the same price as the they would be on Itunes (around $19.99) ?
Do they have any vaulted movies available for purchase ?