All the time. I have back issues to this day from being in an accident 25 years ago while not wearing a belt. I was only going 30 mph. My head first hit the front windshield (cracked the windshield), then the driver window (shattered that) winding up in the passenger seat! All because someone pulled out of a side street in front of me. I was thinking, "she's not going to pull out, she's not going to pull out..." Before I could react, my car hit her front left quarter panel sending me careening off into a high curb and totaling my then Fiat.
Because of that, and the stiff penaltys for not wearing a seatbelt in California, I always wear it. Do I like it? Nope. I can deal with the old lap belts. The shoulder belts are too restrictive for me. I'd rather wear a 5 point harness.