I own the Little Badger and the Double Badger. I have only shot the Little Badger and can echo the previous sentiments about accuracy; this thing rocks! I have put 100-200 rounds through it plinking and while not a formal test of accuracy I was definately impressed. I would have no qualms using it to headshot grouse at 25 yards.
The gun is a cast reciever, maybe aluminum or some zinc pot metal mix but definately not steel. Also has plastic parts (sights and rails) but is metal where it counts. I find it to be a solid, well thought out design with not much I would change.
The Double Badger is a whole other animal, solid steel and wood construction. I am not too fond of the lever action trigger guard to open it but I do like the double triggers. There is no comparison between it and its closest competitor, the Savage 42, a piece of crap IMO. The Double Badger has a solid feel to it that feels goodt in the hand.
There is an "M6" Double Badger in the works, there is a youtube video on it, hopefully someone with more skill can find it and link to it.