I had one fitted with a dynamo hub circa 2008. Friends always remarked on the extraordinary strength of the light, as did the person who fitted it for me. Unfortunately he did not connect it to a rear light. After about three years the IQ head lamp burnt out . I think it needs a rear light fitted in conjunction to take some of the wattage off the front. This year Ultimate Bikes fitted a rear Toplight in conjunction with my new Fly Head Lamp and so far so good. Because it is twinned with a hub dynamo there is no resistance involved when cycling which means you may as well have it on day or night. The only time you must switch it off is in some foot tunnels and at train stations as apparently it can confuse train staff. The main expense in such a system is having a front wheel built with the Sonne hub but it is worth it. My front wheel is so strong, I have twice due to reckless cycling in London smacked straight into kerbs with it and not a dent so it's been a worthwhile investment (£360 all told - gulp).