<choosing my words carefully here because I actually work in a Tier-1 aerospace supplier working on electric aircraft>
.Main one is mass - as a rough figure of merit each of these 110kW motors would have a mass of 40kg plus say 20kg for power electronics, and improving this is hard work. That's 250kg for propulsion, even before you start adding in structural mass and batteries.
Ah - I assumed you were doing a direct comparison of an electric SUV available in a few years to an electric quadcopter available in a few years. Current hybrid SUVs are typically 20 kWh for 30 miles of driving (although most are pretty tepid hybrids incapable of this) - if you go all-electric (permitted for the quadcopter) you can cut out a shedload of mass such as the entire IC drivetrain to get it down to maybe 15kWh without much of a drama - a third of the power consumption of the quadcopter.
More than you'd think, if done properly. The quadcopter example we're talking about, for instance, might well have two motors per rotor with each being powered and controlled independently to ensure that there is no single point of failure (well, it certainly would if certified under FAA or JAA rules - given that they're talking about flying it in Dubai but not under either set of rules rather suggest that some short-cuts might have been taken here). Unfortunately there's a lot I know here about current projects that I can't really talk about, but there is some serious money being put into electric aircraft of all types - mostly hybrid rather than pure battery. The battery type tend to be either tech demonstrators or possible trainer aircraft like the Airbus E-Fan.
The physical avoidance is easier, but that really isn't the problem with self driving cars. Instead the problem is spotting and interpreting a hazard, then deciding what it will do. Controlled airspace gets over this problem by only permitting aircraft with transponders to enter, and insisting that they are under positive control from the ground at all times. To get "flying car" type functionality you need to get rid of this - which either means that everything needs to have transponders/TCAS on board (cue massive revolt from other airspace users - balloonists, glider pilots, GA pilots, hang gliders, etc.) or you have to use optical systems as per current self-driving car systems. With aviation that's much harder however - the threat can come in three dimensions rather than two, and given the very much higher average speeds you need to spot potential threats at a far greater distance than on the ground. It's also worth noting that the maximum rate of deceleration/turning is significantly higher on the ground than can be achieved by anything but an aerobatic aircraft - tyres help an awful lot because they give you positive contact to something that isn't moving, compared to shifting a lot of air to apply a force.
With batteries as the only power source, yes. All I'm comfortable saying is that there is some serious money going into electric helicopters right now, coming from people who know what they're doing.
Getting that airspace will be very painful - no way would "flying car" type aircraft be permitted into existing controlled airspace, and kicking existing users out of airspace that is currently not controlled will also be very difficult. Controlled access highways may actually be easier, since the restricted access interstate/motorway/autobahn system already exists.
Have a think about the cost of inter-seasonal storage of energy - the only plausible way I've yet seen proposed is to use it to generate synthetic hydrocarbons, probably methane. Once you've done that, synthesising jet fuel is pretty easy using standard processes: the assumption that future aircraft will be all-electric is actually quite an implausible one, although they will certainly have a very significant electric component and probably a very large battery capacity (peak power demand
cruise power demand, but cruise energy consumption energy consumption during peaks).
