Since you went with the Blaze, I strongly suggest getting the Planet Bike helmet mount: http://ecom1.planetbike.com/3101.html $5 with free shipping.

Since the amount of light the Blaze 2 watt puts out is marginal on bright days, you'll want to be able to aim it at any motorists you want to alert. In my opinion, under lower light conditions (dawn/dusk and gloomy days) the superflash mode on this light IS bright enough to be useful - especially with a helmet mount. Obviously, brighter is better. I use a 500 lumen flashing light during the day.

Further thought: when you receive it, why don't you throw it on a bike and one of you can look while the other one rides? You can see for yourself if it is bright enough to help with visibility in the daylight. If not, send them back and get something better.