I have an Ol'Man original and my hunting partner has a Summit Viper xls. My Ol'Man packs much flatter, is lighter and very comfortable. The new Ol'man's have fixed a problem whereby the side rails would squeeze you on smaller trees. My hunting partner absolutely loves his Viper. I've yet to try the Viper but from the looks of it, I would say it is very comfortable. Never tried an API but they have been very highly recommended on this forum from those who use em. Neither I nor my hunting partner has had any trouble with the front rail being in the way while bowhunting.

I don't think you could go wrong with either the Ol'man, API or the Summit. If you can, try em out at a store and then just go with the one you like best.

-Mike