Blizzard has had this for a number of years, at least for World Of Warcraft. You can start playing and it downloads the rest of the game in the background. I th

Blizzard has had this for a number of years, at least for World Of Warcraft. You can start playing and it downloads the rest of the game in the background. I think the loading screens are a bit longer since my guess would be that the program checks to make sure the needed files are there for the zone and, if not, it downloads them as a priority.