I had a terrible accident in November. Without my helmet, I would have undoubtedly died.
As it was, I broke my neck and hip. Unavoidable injuries because they were from impact. But I was protected from the worst of skin problems and major other breakage by my other gear.
I always wear specially designed street pants and jacket, as well as boots. The accident shredded my boots, but not a drop of blood on my feet. My pants, Icon denims with kevlar-reinforced knees, took all the scrapes that would have flayed my legs. My jacket, another Icon item (Hooligan Battlecry, black and red) kept upper joints and possibly even the collarbones and definitely the spine safe. My full-face Sparx helmet was destroyed--but I didn't actually get a concussion after being thrown 18 feet and sliding another 30, and Sparx replaced it for free on its warranty program.
I think it should be emphasized that, while leather pants may be the best protection against abrasion and all kinds of other stuff, all the Kevlar and Kevlar-reinforced gear available for street riders, especially that available with CE armor at joints and along the spine, is far more protective than any foam could ever be. It's also a great cost-effective alternative if your budget won't allow leather. The armor in my jacket prevented a total break in the shoulder I landed on and in that collarbone. There was one small scrape on my hip where my slightly oversized pants got yanked down (the pants were later destroyed by medics cutting them off).
After several months of PT and gutting my gusto back up, I started riding again (albeit on a 250 instead of a 650 until I become more proficient). I can't emphasize enough how thankful I was that I was taught to wear appropriate gear at all times (it had been a beautiful day and I had considered wearing tennis shoes and no jacket).
This is more than a comfort issue for us--my husband told me to consider your gear the doors and interior of your car. You wouldn't drive a car that was structurally completely unprotected. Leather is an incredible, durable and very protective material, but should be used in conjunction with armor to save those pesky out-poking joints in case of an accident. And mesh, very nearly as protective, is a lot cooler in the hot months.