Just beat the game today. It was really good, had a bit of a different feel than the other but I think that's why I liked it. I feel like it has good replayability and a good story. In a sense it was easy than the others but it was still a challenge in some parts too. I had no issues with graphics or any bugs. Worth a play through if you like the Pikmin collection.
I will say I did not play any kind of Co-Op so I can't give a review on that. I've been a long time player since Pikmin came out on the Game cube and I can see why some people don't like this much as the other ones. I don't see the point in comparing it to the other games. Just think of it as just a new type of Pikmin game.