Outcast is good pontoon boat. I have a nine footer and it has been great. They are a good company. Although I have never tried the Cougar it seems like it would be a pretty stable boat. I like the pontoon set up. I would like to know how it does on rivers. A buddy of mine has attached a trolling motor to his and it does pretty good. I don't think you can go wrong with it. good luck and if you get one let us know how it does on the river.
I've had a Panther for a year now and find it a pretty good boat (for the $'s)
I haven't seen a cougar in person but it looks like they are an 8' version of the 9' panther (only sold @ cabelas). That said; in this price range I would also look at the Scadden Box Canyon.
I've owned my Cougar for the better part of a year now and am really pleased with it. Easy rowing, stable and low profile. Light and small enough to fit into the back of my 86 Vanagon fully assembled or on a rack on top of my Beetle. I have used it in both fresh and salt but have yet to float a river in it. So far, no problems with it.