I used to drive a 6 wheeled Amphicat - and loved the thing.
It would go virtually anywhere that I wanted to go while hunting and fishing. It wasn't a fast vehicle that you'd use to race around the fields, but in the bush, it could do anything short of climbing sheer cliffs.
Generally, I didn't have to cut trail to get to a downed deer, since it could run over or push down almost anything I came across. It had a zero turning radius, so even in the mature bush I could get by without cut trails.
Muskeg and beaver lakes were only a problem if I got hung up on an unseen stump, and even then, a little manipulation could get me unstuck.
Since I rode "inside" the vehicle, the centre of gravity was much lower, and I could climb or traverse inclines much steeper than a 4 wheeled motorcycle could hope to handle.
The only reason I haven't gone back to one of these "true ATV's" is the cost. They're a little outside my budget.
Where I hunt, all the camps are on wilderness leases, and accesss is via bush trails that feed into one another, and finally go to a road the trucks can access. Two years ago, on my way out, I met another gang who were using 2 8-wheeled argos to go out. As I travelled behind them, and saw how easily they went through some of the tougher stuff on the trail, I became a little overconfident. When they went through one big waterhole without even slowing down, I plunged in myself, and promptly got stuck. I'd forgotten the limits of my 4 wheeler.