I have a Summit Viper and love it. It isn't too heavy, around 22 lbs. Really it's annoying when you've got that thing on your back and you're dragging a deer out of the woods.
Sometimes it can make noise while walking, you can stop and adjust it so the bars stop banging into each other. For the lightest option, you can't beat one of those lock on or hang on, whatever they're called. But the wide open area just doesn't make me comfortable. That Summit has you completely enclosed and it's very comfortable to sit in.