My wife and I bought an Ameristep Penthouse just before this last Spring. It has worked very well for us and is HUGE! I am 6'4" and not skinny by any means. We can both sit in it and have plenty of room to draw and shoot, at the same time if we wanted to. I can stand up and stretch or shift my chair for a better shot angle. It even has zip-open windows for standing shots.
I have a Double Bull as well. It is a really good blind. I am not fond of the corner entry though. Since I am a big guy, I nearly tear the thing down just trying to get in. The Penthouse has a full side, zip open door.
I can't argue that the Double Bull is made with better materials, but I can buy three or four of the Ameristeps for the Double Bull price (we got ours from Amazon.com for a much lower price than ANY other dealer). We just retired an Ameristep Doghouse blind after using it for 8 years (door zipper finally gave out, can still be used with some repair). Following that logic, I can get 24-32 years out of 3 or 4 Ameristeps for the same price of the DB. I really don't think the one I have will last that long.
The DB does have a quicker set-up; again, no arguement there. We set up our blinds before season and brush them in for the whole season then take them down afterwards. So set-up time is of no consiquence for us. We don't worry about brushing for Turkey season.
I would recomend trying them out at the store. Get in, move around, then subtract HALF of the room in them to allow for bulky clothes, packs, bows and misc. gear and chairs.
You get a little bit of a view of our new blind in these pictures. These are our 2010 Spring Gobblers, both shot in the same day from the same set-up; about 6 hours apart.
Good luck with your hunting.
OkKeith