A friend has one and allowed me to shoot it one afternoon. My primary and backup guns are both 391's and I shoot between 15,000 and 20,000 targets a year.
The front end of the A400 seemed to be a bit light and whippy for me. However, if I was going to walk all day chasing upland game... it would be easier than one of my Optima bore 391s.
The felt recoil was less than my 391 as well... at least to the shoulder. On the other hand, the gun I shot had the additional kickoff feature. Which is nice but I personally am not a huge fan of the stock sliding back and forth across my face as the recoil reducer compresses. It would take some getting used to, and surely in time it would probably go unnoticed.
Seemed like a good gun, cycled my light loads, shot where I looked, and generally I liked it a lot other than the points mentioned above.