Some pre-answered questions:
- Yes, this is all DriveThruRPG/RPGNow with a different skin. Your account with those sites works for this one.
- Yes, if you bought D&D PDFs from DriveThruRPG or RPGNow before, those are back in your libraries and can be downloaded; you don't have to re-purchase them.
- All extant editions of D&D are supported and present (or will be).
- No, I don't believe "D&D Next" will be on there, at least not for a while after it launches.
All for now.