From playing other checkpoint based games, we are used to repeating some areas of a game over and over. But normally, these areas cover some minutes at most. Not here. It can be easily up to 30-45 minutes you have to replay after dying the third time in a row. This might be fine for the few masochist players around. For me, it's no fun at all, it's just VERY boring.
Worse thing is you cannot just quit the game when you want, because this will also force you to restart a LONG way back. To sum it up: if this game had five times the number of checkpoints it has now, it could be a nice game. In the current state, it's for hardcore players only.