I think the "you die in your sleep, you die for real" thing is an urban legend. I died a few times in my dreams, even saw my "gardian angel" once. It's more a symbole of change then death.
Come to think of it, it's been a while (as in years) since I flew in my dreams.. wo.
Flying is the most common theme in my dreams. In nearly every dream I've had over the past decade I've been able to fly. It's as normal now as walking around when awake, and I have to admit I'm sometimes disappointed I can't actually do it in real life, because in my dreams it's normal for me.
It's never true flying either, more like controlled floating, and once I'm floating it's hard to get anchored to the ground or floor again. I can't go too high outside (maybe because my brain can't process what everything would look like from an altitude higher than a treetop), sometimes I have to "swim" through the air with my arms and other times I can just do it by thinking. Every once in a while I see something happen that makes me open my shirt to reveal a blue suit with an S inside a diamond
I want an invention that lets us video record our dreams. If you think about it it should technically be possible, since they're neurons firing off inside our brains.