As for safety checks on drivers and such, the last time I used a taxi, which was last summer, it was a local company I'd used before and the driver they sent was in his own car, no taxi plates, no meter.
I didn't think minicabs needed a meter (in most places), I thought you just agreed a fare in advance (when booking, as you can't hail them). They should display their identification and details though.
I don't agree with some of Uber's practices re employment and taxes but these are things – as ever – that governments have control over. That are, after all, responsible for the loopholes that companies expose. That said, black cabs in London are precious about their monopoly and London is rather unusual – in most countries (other than the far-east), taxi driving is a immigrant job. The knowledge, of course, is one of those tools used to keep out new entrants. A level playing field should be level for all, not favouring the current black cabs.
The consequence of taking a lot of cabs off the road (though I'm sure Uber will figure out how to stay on the road) is that more people will use illegal cabs, because black cabs are uproariously expensive and never around when you need one (try hailing one at 11pm; however, they'll spend 9am-10pm blocking up every street in central London).
I've always used Uber abroad and never had some of the issues I've had with local firms (overcharging is a tradition, I've lost track of the number of countries I've been overcharged in, before Uber I used to book cars in advance).