I like this mostly just because there is no massive amount of life gain, I put them main because you never know when some welder/metalworker/big dude needs a time out.
I don't know. I'm just very apprehensive about giving them a free land. My rough statement right now is that I'd play Swords to Plowshares in a Rod Fish/Mana Denial deck and I'd play Path of the Exile in a Vial Zoo/Aggro Tempo deck. The life gain is the suck when my win condition is killing quickly, but the free land is the suck when my win condition is control + mana denial.