I've got a NiteRider Lumina 700 that I'm pretty happy with. It has a retina sear setting (high = 700 lumens), but I usually just use it on medium (350 lumens) because that's bright enough without actually making drivers look away from me (which the high setting does).

I do think it's a good idea to also have a helmet mounted light, because you can easily aim it wherever you want. I have a Blackburn Flea for this purpose. It's very lightweight and reasonably bright for its purpose (~100 lumens) but the recharging mechanism is awful (exposed contacts which corrode easily and therefore need frequent cleaning).