Downside: Not a lot of freedom of travel... You need a crew, a motorboat, and it requires a long hose line (and powerful jet pump) to feed the H20 propellant. Also, you won't be able to wear a tuxedo like James Bond and drop in on friends—well, you can but you'll look like the cat dragged you in—swimwear fashions only. (Now if you friends live along the waterfront, then sure, why not?)
Upside: No FAA pilot's certificate required. It's safe to fly with nearly unlimited time in the air with flights up to 30 feet in altitude. Test flights are available in New Jersey, Florida, Nevada, and California and range from $170-$250 plus for 30 minutes, including 10 minutes of flight instruction.
You can purchase your own, complete one-person jetpack kit for around $10,000.