What color is your helmet? I wear a white helmet, which is noticeably cooler (in temperature if not in appearance) than the dark green helmet I used to wear. It is also more visible, which could be helpful--and I have front and rear lights on it, originally for better visibility as my head is higher up than the trike (or bike), and has the additional advantage that whatever bike or trike I'm riding, I have lights.
Back when bike helmets first appeared, we all thought they looked dorky and resisted wearing them. Since then they've been styled more attractively, and we've gotten accustomed to wearing them. I wear mine almost every time I ride, whether on bike or trike. Better to be a live dork than a dead hipster. The debate over whether they really make a difference is more about people resisting the "domination" of wearing a helmet. Last week a motorcycle rider in an anti-helmet protest group ride fell off his bike onto his head (at low speed) and was killed by head trauma. There were people commenting approvingly that he died for his freedom. Personally, I think there are freedoms more worth dying for than the right not to use a piece of safety equipment. The thing is, you won't know if it makes a difference until you are in an accident, by when there is nothing you can do about it.