A cowardly friend of mine has pointed out that the character in Heroes with multiple personalities actually does have a super power when she is in her alternate personality.
The fact that they didn't have the time to show this is further proof that the show doesn't have enough budget and is trying to do too many things at once.
Heroes is one of the many shows trying to capture the market share of Lost by replicating the entire feel of the show. Unfortunately, they've only mastered the part of Lost that I hate: the endless wasting of time. It's not against the rules to have non-trivial events.