I always wear a helmet, always have always will. But it should be personal choice for the reasons mentioned above...
I have a mate who doesn't even own a helmet, cycles way more than me, never came off even once. I also have a couple of mates who've had possible life saving experiences due to wearing one.
The first one, was stationary at a set of traffic lights in Edinburgh, clipped in to his SPD's (fancy pedals locked to your shoes). He toppled over side ways, hit the kerb with his head, split his helmet into multiple pieces and concussed himself. Paramedics asked if they could keep his helmet (or what was left of it!) for their safety talks!
Second mate was at Glentress mountain biking. Stopped for a break and moved sideways off the track to let other riders past. Again lost balance, toppled over, came to rest with his head on a rock! Shoulda seen the nick of his face, wasn't pretty!
Actually, I have another mate, very experienced mountain biker who was showing us some routes up the Pentland hills near Edinburgh. His rear wheel slipped on some wet tree roots and he shot of a gorge
He hit the far side full on and slid to the bottom (only about 12 - 14 feet deep). He walked away from it injury free (apart from all the bruising!). Probably would have been a completely different story if he had no helmet on.
Talking of Glentress, me and my son were there once and seen a guy with a full face helmet on. You could clearly see through the front that half his face was scraped off - guess he learned the hard way
So yeah, apologies for the rant but I never leave home without mine...