I've wanted something like this for a long time. It does weigh more, so Lance and a lot of you probably won't use it.
My head is just a bit bigger than normal. These helmets have such a nice way of adjusting for size. You just rotate a dial on the back of the headband.
I got one big enough to fit a toque under in the colder weather. (The word 'Canadian' is at its most impressive when you put it in front of 'winter.')
It is over 500 grams but the shell looks like it will stop the first couple of bullets that hit it. Have had it for a couple of weeks now. It does get a bit sweaty but my commute is only 6 miles so not a problem.