To me the problem with the Five-Seven is that the average person can't get the ammo that makes it into what it was designed for, defeating Kevlar vests. It's not a small gun. There are countless other pistols as easy to conceal if not more so. If capacity is the main concern, 9mm is much cheaper and I could get an XDm for close to half the price and have 19 rds of 9mm, pick your weight and loading. It would be much cheaper to practice with too. Granted it would be heavier, but personally I'd feeling more comfortable with SD ammo out of a 9mm than the commercial 5.7mm loadings. Just my 2 cents.
Know the status of your weapon
Keep your muzzle oriented so that no one will be hurt if the firearm discharges
Keep your finger off the trigger until you have an adequate sight picture
Maintain situational awareness