Flashing lights do attract the attention when you're in town. The highway code advice regarding not using them outside lit areas seems not to be adopted round Harrogate. Like many people I drive and ride and doing both gives you that reasonable perspective ;-)
The thing that really gets on my back is the folks riding out in the country with very bright flashing lights that are badly adjusted. You are driving along and you get a bright flash that dazzles you and then blackness followed by another bright flash and so on. We can now buy Cree lights that are brighter than many car headlights, I don't want to discover that the light on my bike has just put an oncoming driver on a country road in a situation where his vision has been affected. It might be me he can't see because of the dazzle. As others have said you can't judge where the oncoming bike is or how fast it is travelling with flashing lights either, our brains lose track when the light is off.
When a car has an MOT, the alignment of the lights is checked to make sure they are not causing dazzle for oncoming cars and drivers *should* dip their lights when oncoming traffic arrives (yes I know there a number who don't). I check my lights when I go out on the bike and I don't have the light flashing out on country roads at night.