You're lucky if you do over 20mph in London anyway so I don't see that as a problem, but it is a simple but effective method to try and tackle the growing poor air quality in London. They'll never close down airports just because she was mayor and the congestion is a filthy tax anyway.
As for London...it's great if you like it, but personally, I have no love for it nor do I see myself ever going back there. What it offers can easily be found elsewhere and in a much better environment. If you want proof of that, recent studies have shown that quite a few cities around the UK have come out on top of London in many different ways. In terms of best capital in the UK, Cardiff (Wales) comes out on top in almost every department.
Better yet tackle the technology not the consumer base. I think it shows how much experience you have in London if you think doing 30 mph is rare, I'm regularly doing that and the only time it falls to that level is if I head into Central London... which is what public transport is for.
It was in her manifesto, don't matter if they would or not it just shows a detachment from reality. Not going to deny the congestion charging isn't terrible but it further proves how bad her ideas are if she thought it was a good idea to push for it all over London not just the centralised areas.
It comes down to personal preferences which city you like more but on average I have to disagree, what you find in London cannot be found easily elsewhere and by that I mean pure multiculturalism. You can't find areas like Southall or China Town easily elsewhere in the UK and in terms of parks, universities, sports entertainment... London just has a monopoly on most of these factors because of its sheer size and population.
That's not to say the other cities such as Edinburgh are bad (which to be honest is a closer rival to London than Cardiff in terms of historical design and heritage) but they have a completely different feel to the city. To describe it as a joke is excessive and people just wouldn't flock to the city if it didn't have anything going for it.