I think this is definitely something subjective, there's certainly an appeal in difficult games, but it's not for everyone. This is one of the things that you have to decide early - if you're making a difficult game you're consciously making a product only for a specific group of players. And that's perfectly valid, I think.
The pros that the OP listed are kinda off, but the first one about a sense of accomplishment is totally legit. It's one of the many reasons why I love challenging games.