Originally Posted by
Mr. Safety
I get that. I think running 16 lands, with the option of Jet filtering through extras, is close to optimal for testing. If my hand is one mana short of going off, finding a land isn't a bad thing either. A full yard, 4 lands, and Past in Flames is not a bad situation either.
The danger with Magma Jet is: do you keep a land without Mountains and count on a Lotus Petal/SSG to fuel Magma Jet to get you there? It's risky business. I would say mulligan that hand. I think Jet falls into the same category as Probe really, it just does more. I have kept openers with double Probe/no lands, but even that is pretty edgy. However, if there is a window where you play Jet to set up your next turn it could be amazing.