High difficulty does not necessarily mean frustrating experience. I mean potential frustrating experience. Because every player is different. VVVVVV and Super Meat Boy are extremely difficult, same for Super Hexagon. But they offer checkpoints and / or instant replay for the sake of flow.

The programmer of SMB explains their system in "Indie Game: The Movie" and I think it´s a real good approach. In the german Making Games magazine issue 3/12 there was a nice explanation of it, too. It boils down to "frustration is removed by shifting from losing lives and replying a whole chapter to having unlimited retries in rapid succession and keeping the level goal in sight"
I think the last part of this conclusion is most important.

Just some thoughts of a grumpy old man, don´t take me too seriously.