I will ride with 200 but I'm not happy about it all the time. That's the medium setting on my cheap $15 flashlight. I'll use that when it's already getting a bit light or the moon is out helping a little.

In general I want 400 to 500 to be reasonably happy, 700 makes me perfectly happy. I have a "1600 lumen" front light from eBay ($35 last fall) which I estimate actually puts out about 750 lumens, which is fine.

My light is similar to the one cyccommute links to above. I recommend getting also a beam spreading lens.

A light like this:
http://www.ebay.com/itm/290930407139
with this lens:
http://www.ebay.com/itm/271236305324

Or if I were feeling particularly flush and/or wanting to support non-China manufacturers, I'd go to Action LED Lights and buy a Gemini.