I ride mainly at night and have a stock headlight. I used to have a 10 watt Mtn. bike headlight I would wear on my helmut but it slipped off and got eaten by my rear sprocket, lost forever. A helmut light is key to riding at night so you can point to see where you are gonna go and helps when going over logs. I was able to ride a gear higher with the helmut light too. I think the next one I get will be the double light by I think is Night Sun, one is 10 watts and the other is 15 watts and I'll wing nut it on to my visor this time.
It would be nice to have a brighter headlight too.