When the material sciences are to the point where a lightweight container can sustain Earth atmospheric pressure from crushing down on it, we'll have a practical way to take off vertically without prompting your neighbours to invest in surface to air missiles when you crank the engine on one of these in the morning on your daily commute.
Except that the density of air is ~ 1.2kg/m^3, so to produce 100 kg of lift (average weight of an adult male American: 90kg) you'd need a balloon with a volume of 100/1.2 = 83.333.. m^3.
If your balloon is a sphere, the diameter should be 2 * (83.333 / (4*pi/3))^(1/3) = 5.42 meters. Google tells me that's about 18 feet.
I suppose it would be feasible for recreational activities. Commuting into a city? Don't think so.