There are some unfair enemy placements, and the boss patterns are fairly unreadable and quick at times, but this is a Kirby-venture, and it looks stunning on NES for being one. It's by no means an unfairly difficult game, but it might just challenge you a bit compared to other Kirbs.
Just remember, if you're on Switch, the - button is the one that takes away your ability. I learnt that on the 6th World and I felt pretty stupid. ;-;