Yes, I have. But, call me crazy, I see games as games, not chores to slog through or feats to overcome, and always have. Fun > difficulty, and satisfaction > bragging rights. I've played through many a hard game in my day and generally enjoyed it, because that was how things were done. When you jumped, you always jumped the same height as you did the last time you jumped, and when an enemy hit you you got knocked back the same number of pixels. These days when games have too many physics-related variables and such, rigid lives-and-continues systems just don't fit. Especially in a game about physics.