RE: summit viper..
I LOVE my Viper. I mean, I actually LOVE it! It is sooooo easy to use. It attaches to the tree quickly and quietly, (though it does make some noise, especially if you are really in a hurry) it's very easy to ascend and decend, and man.......good luck staying awake! I would rather sit in my Viper than my Lazy Boy, and that's no lie. The one problem I do have is that it grips the tree a little too good. Sometimes when decending, you have to pull it off of the tree because the teeth have sunk in.
But, like any climber, it's fairly picky of the tree it's in. You can't just put it on any old tree, it won't work. The more uniform the better. Also make sure you start out with the stand at an incline so it can level out as you climb. Climbers aren't w/out their problems, but you'll love it too.