Alright, so it seems the consensus is that
1. First round you cast it and hit, target takes damage or half damage on a miss
2. On target's turn, he does not get a save.
3. On your (second) turn, you may choose to maintain as a minor action, whether you hit or missed. If yo do, the target and all adjacent take damage.
4. On target's (second) turn, they get a save at the end of their turn to end the power. If they fail, return to step 3. If they succeed, the power has ended - no more saves or sustains.
If the power did not cause damage on a hit, I understand this won't be changed one bit. So you could miss on your attack, causing no damage, yet causing "secondary" damage on subsequent rounds.
I also understand that it is impossible to maintain on the first round. You need to wait till your next round in order to sustain.