I've gotten the heels of my hands scraped down to the meat 3 or 4 times in my life, but only every hit my head once. IMHO gloves are at least as important as a helmet. Fully healing the worst palm injury I've had took almost 3 months. 1.5 months of that I had very sensitive (RAW) palms; this means riding hurts, and for a programmer it's not much fun to work either.