Actually, given the amount of stories that came from killing off Gwen- a character that wasn't really that popular with the readers, and whose relationship with Peter Parker had reached a dead end- actually gave the series a shot in the arm. Peter's relationship with MJ was hardly one of ideal fantasy, as MJ's growing realization and evolution as a character took her away from the sexual fantasy she had been before and into a fully fleshed out character. She may have been a fantasy before, but she wasn't after Conway grew her into a more well developed character. The death of Gwen led to the death of Norman, as the editors (Who also agreed to the death of Gwen, and who disagreed with Conway's first suggestion of Aunt May) felt that Norman needed to be punished for Gwen's death. This led to Harry becoming the Green Goblin, which saw him eventually becoming a more strong willed character who made his own destiny. It also led to the creation of the Hobgoblin, one of the most popular characters in the Spider-Man mythos.
The easy way out would have been to just do what was done with Betty- move her off the stage and into limbo. Killing Gwen, in a day and age when comics still had their innocence, was the real risky move.