There was just a discussion about this on the SJ board.
I think they have their place. I use them only for snow trips, and for really long treks. For Whitney, I leave them at home, unless there's snow. They're good for balance on snow, and for leverage when you posthole. When I do a prolonged uphill hike like C2C, it helps ease the strain on the quads going up, and the knees when going down. For most hikes, they get in the way.
I would not spend $150 on them though. My cheap $30 pair works well enough.