Voom can't survive as an HD only resource. They can survive only by offering the most popular channels and an outstanding HD package as a bonus. Although growing, the number of HD TV's is not great. Most people could care less about HD. I consistently find my wife watching fuzzy Distant networks, when with only the flip of a remote, she can have them OTA in HD. I think most people are of that mindset. Sure, when we do get the HD on, she's like wow, or thats pretty. But it's not a priority.
I don't think Voom needs to offer crap like Bingo TV or 50 shopping channels, but to compete, they are going to have to offer the most popular channels, the most HD, the best Picture Quality and a DVR, and then be ready to loose money for several years to become profitable.
Once they start yanking subscribers from D & E, they might start adding HD, improving picture quality, etc. Then Voom may be in trouble again, the others have major infrastructure in place and are ready to battle.