Late game difficulty is quite challenging but its mediocre at its best..
Gameplay at first sight is good(reminds me of Azure Dreams on PSOne and Izuna on DS) but gets dragging later on as missions are more of the same. Getting help from friends on missions are good but that's just about it.
As most Pokemon games out there, you gotta catch 'em all or specifically gotta "befriend" 'em all. And its usually a nice thing since I've wasted almost a hundred hours just to collect what the game has to offer. But I've got no regrets there. Maybe because its the only game where every legendary pokemon from Kanto to Hoenn are available.
All in all, as a dungeon crawling game there's nothing new Pokemon Dungeon: Red has to offer but if you're a big fan of Pokemon better go ahead and try it.