I like that more, how about this?
SUPERNATURAL STEALTH [-2]
Description: You are supernaturally stealthy. Seriously, what did you expect?
Skills Affected: Stealth.
Effects:
Imperceptible. Your Stealth is never penalized due to movement, cover, or environmental conditions. You may hide just as effectively while running through a bright hallway as while lurking in a shadowy corner.
Hard To See, Hard To Hit. You may use Stealth to defend against physical attacks. When dodging this way you may add Athletics bonuses from Speed Powers to your Stealth skill. However, you may not use Stealth bonuses from Cloak of Shadows or other similar abilities.
Perfectly Consistent. When rolling stealth for hiding, skulking, or sneaking, you cannot roll below a -2(-1?).
Invisible Attacks [-1]. When you make a physical attack, your Stealth supplements any attack you make.
Superior Supernatural Stealth [-1]. When rolling stealth for hiding, skulking, or sneaking, you cannot roll below a 0(+1?).
I'm not a fan of the alertness modifier on Hard To See, but I don't think it is game breaking by any means. I liked your idea of limiting how bad a person could roll. Superior Supernatural Stealth could increase the floor boundary instead of adding a flat bonus. I also changed Invisible attacks. Before someone could have Stealth and Fists at 5, and their opponents would almost always suffer a -1 to defend, essentially resulting in Fist attacks starting at 6. Having Stealth supplement attacks encourages people to have Fist and/or Weapons start at 4 or lower. This is minor but I think Stealth Powers should affect combat more indirectly than Strength/Speed/Toughness powers. Thoughts?