Originally Posted by
Aggro_zombies
The issue is that it also prevents you from attacking while eating up all your lands, so it's not like you can use it to cover for counterattacks while rumbling in with large guys. If your intention is to buy time, it's pretty bad because you're losing mana production to it while not really answering what the opponent is doing/has done. You could try to Assault the other guy to death, but that becomes increasingly difficult the longer you have to mess around with Chasm - unless, of course, you want to pay the upkeep. But that can't always be done.
EDIT: On the other hand, you could retool the deck to be more like a Lands/Aggro Loam hybrid by running Exploration and ~30 lands or so. This is an interesting option, but you're trading one of Lands' strengths (difficult to interact with) for a better clock - but in a format as adept at answering creatures as Legacy is, it's not clear to me that it's worth it to make that trade. I can maybe throw a sample list together later if people want, though.