One downside is the risk of sunburns, and it's almost a guarantee that you or someone you know will get a burn. It's no fun, and for the repeat offenders it can be detrimental to your health - repeat sunburns can increase your risk of developing skin cancer down the road!
If you find that you have involuntarily slipped into a lobster suit for the next week, you will first want to minimize your exposure to the sun until your burn subsides. Reducing re-exposure dials down your risk of re-burning, as well as the aforementioned risk of health concerns down the road. From there, it's really a game of pain management. Depending in the severity of the burn, you can take some NSAIDS like Advil (ibuprofen) to dull the pain. Also applying a topical aloe can soothe the skin during the healing process. Make sure to heavily hydrate in the healing period - your body is healing itself, and will dry out quickly if you don't replenish with plenty of water!
Once you have healed up, use some preventative measures the next time around. Avoid prolonged exposure between 10am to 2pm, when the sun's rays are most direct. Also get a hat on to protect your dome, and as unappealing as it seems to many people (myself included), throw some sunscreen on.