I got the Bushmaster a few years ago and didn't like it at first. Last year I got a Viper. It was the last one in the store and was an open box. I found I was missing some pads, documentationand the CD. Wasn't sure what I else I might bemissing. I called the store, they called Summit and Summit promptly sent out the whole bag of stuff that comes with a Viper.

I really liked the way climbing stirrups worked on the Viper. Since I had an extra set that came with the bag of goodies I put those stirrups on the Bushmaster. Made a world of difference. Much easier to climb now.
The Bushmaster seat is very comfy and so is the Viper. The Bushmaster packs a bit easier than the Viper. I like the rail on the Viper for gun hunting and like having no rail for bowhunting.

Be sure to check out the stirrups. They make things much easier.