Even an ugly helmet is better than no helmet at all. I agree with Don that you should go to a bike shop and try a few helmets on before you buy one, particularly if you are someone who rides a lot of hours each week.

I'm not such a big fan of the skate-type helmets. They are heavy as hell, and if you often go for rides lasting more than an hour you are going to hate wearing one. I don't really think anyone over the age of 16 thinks skate helmets look more stylish than cycling helmets, but they are more durable, and easier to decorate with stickers if you are into that sort of thing.

I've been in enough bike wrecks (2 of the 3 ambulance trips I've had in my life were the result of bicycle accidents) to know better than to go without wearing a helmet. One wreck resulted in a good concussion and a case of short-term amnesia. Had I not been wearing a helmet it would likely have been much worse.