I think my success on the eastern front is responsible for my victory this game. I had Joe on the defensive until I controlled most of the good terrain around moscow. I kept moscow surrounded and let Joe/John try to push me out of the woods and forest. Vyazma in particular is a place where 100's of pp worth of metal and flesh is just lying strewn about in those woods. As long as I had Moscow under siege the bulk of russia's forces were tied up. Around the beginning of 44 I stopped reinforcing the eastern front and slowly let Russia lose lots of forces assaulting me in the good terrain.
In Italy, Tyrol proved to be an incredible defensive spot for me. I could build directly there and it is in the mountains. I placed a build there mid 44 and cut pattons forces out of supply all the while ignoring the fact that rome was out of supply and in peril. I knew that rome couldn't be taken based on the forces left on the board for the allies. If they wanted rome, they could have gotten it with a concerted effort. But taking it would severely hurt efforts in the north, which I was more worried about.
I had a rough time taking norway but i don't think it was a game breaker. I only lost troops. John's statistical blunder in north africa when he lost 8 tanks to a handful of infantry and support was particularly painful to watch.
I think the attack on Norway in the endgame wasn't worth it for the allies. My north french and german coast was a little overdefended at that time though so I don't know what I would have done. Maybe a concentation of forces for 1 assault at milano or marseilles could have turned the tides enough for victory.
I also think that it is impossible for the allies to win through vps after Summer 44. I also believe the allies will lose if it gets to winter 44 at all. The allies must take Berlin before this point to have a reasonable chance at winning.