It's a Dinotte 400L - but now I want a DesignShine. Apparently the DesignShine makes the Dinotte look like a Cateye rear light, i.e. just about invisible. The Dinotte is quite bright, but not soul-destroyingly so. It's probably not remarkably different to car brake lights, but the flash pattern makes it considerably more offensive than the fixed-on setting.
Must admit I felt a bit guilty about forgetting to turn it onto a group ride friendly setting on that ride, and on the more recent one with h_W.
I'm slightly sceptical that the Phillips light Simon is on about is really that good. I mean I'm sure it's a very good light, but I'm sceptical about it having any chance at all of competing with a modern super light like teethgrinder's Exposure SixPack (2000 lumens, almost), or even a more down-to-earth MaXx-D. Of course I'm with everyone who thinks that our LED lights really ought to have better optics closer to those on car headlights to allow for proper dip and full beam settings.