I'd love to buy a Zero (linked lower in the thread) if I had a safe place to store it or some good insurance (motorcycle theft is common in the UK).
WRT weather and other concerns - frankly, the time saved by riding a motorcycle in a congested city blows that out of the water, IMO. In conditions other than gridlock you can maintain an average speed ~50% higher than all other traffic.
I'd love to see electric bikes go mainstream because I think they address almost all of the concerns people have about cycling (sweaty, no good for the unfit/disabled, etc).
You can park 4-5 scooters in a car parking bay, tuck them away at the side of footpaths and in front of stores, if the roads became populated with them it'd possibly double or triple throughput for single riders.
I currently own a 125cc motorcycle and it's a godsend. Especially in the summer months it turns commuting into a joy, and reduces the time taken to perform errands by 5x over public transport (there are plenty of places I can ride to in 20 mins or take a combination of buses and trains to get to in 1.5 hours).
I think living in a large metro area for an extended period of time would be unbearable for me without owning a motorcycle. Most cities have radial transport networks - concentric journeys outside of the core have ridiculous routing as a result.