Kael Hate, Zanzarino has made a point of mentioning in chat that targeting wasn't the right word to use for Immaterial/Burrowing -- but until he clarifies it on the cards, I guess we're kind of stuck with what we've got.
avidteen13, it would (as mentioned above) nullify damage from Eagle's Eye, Fire Shield, Thorn Carapace, Unstable Gas, Fire Storm, Plague, Virus, Bloodsucker, and Toadfish.
Terroking, that would be OP in my opinion, because it's basically like Momentum plus the better part of Quintessence -- if the enemy doesn't have a spell that targets your creatures, he's screwed. That's a bit beyond where I want this to go.