I picked up an 870 police afew years ago for around the same price as this and have had no issues with it.
As much as concepts like this are interesting and have there place I do not see it replacing the 870 or the 500/590 in the hands of Police or Mil even if it was perfect. 870 is tried and trued reliable, and you will always find parts for it.
Just my 2 cents.
My two cents is the 500,590 & 870 were all new once too.
My Gen4 runs like a champ