The issue with helmets is complex. Anytime a human head gets jerked around violently, the brain inside it is going to hit the inner walls of the skull with dangerous velocity. Long term exposure to repeated inner-skull bashings lead to traumatic brain injury, whether the victim habitually wore a helmet or not, so rugby players are a risk of traumatic brain injury, too.

The problem with helmets, and which, I think, makes them more dangerous to wear on an overall basis, is that when you get hit wearing a helmet, the damage is two-fold; your brain is still hitting the inner wall of your skull - but the entire head is actually hitting the inner sides of the helmet just as hard, as if the head itself were a brain being bashed around inside a skull. Voila - more damage!

And of course, people who wear helmets are apt to be far more reckless because they're consciously or subconsciously thinking that they're safe because they're wearing that helmet.

And yes, the multiple lateral passes I saw rugby teams make again and again was the first thing that impressed me. If you ever have half an hour to waste (because I wouldn't suggest you watch an entire North American style football game), watch a few minutes of NA football and watch how narrow a range of action options the teams employ.