I'm not even that bothered about it being illegal - just that it's bloody dangerous and they could quite easily injure or kill someone while they are jabbering away on that obviously life-or-death important conversation. Every day on the way to work [disclaimer - by bike, but I do drive, and no I've never used a phone while cycling or driving even before it was illegal] I spot at least one of the dangerous eejits, and if I'm stopped at a junction and they are passing I've taken to waving at them and trying to gesture in a phone-miming/head shaking way that what they're doing is not a great idea.
Several times I've been told to basically f-off, and one woman in a rammed supermarket car park started having a lengthy debate with me about how it's not illegal because it's not a public road. Well maybe so - but there were lots of pedestians wandering in the middle of the aisles, small children, cars darting in and out of spaces - maybe she'd like to actually focus on her driving? She was steering around the ends of the aisles one handed, chatting away, and I was literally wincing as she did it. Why isn't mobile phone driving socially unacceptable in the same way that drink driving is now? Why do some people think it's a perfectly normal thing to do in broad daylight as they drive around busy city streets?