MrNE,
I own a Krieghoff Classic Big Five in 470 NE. I like the gun a lot. It's accurate and handles well. The cocking decocking features works fine and doesn't take much to get used to.
I've only fired a few boxes of shells so far from this calibre but it functions flawlessly.
I also own other barrels in other calibres for this gun. These have proved themselves worthwhile and a lot of fun to shoot. It makes this gun more rounded and thus more useful.
I'd buy it again in a minute.