Your eyes will adjust to the area of the light. For example I took my bike on the local bike trail just before Dusk last month. When I went through the Staple bend tunnel, I could barely make out the tunnel with the light, but when I went back through it after dark (and my eyes had adjusted for the dark) the light lite up the tunnel very while. The difference was almost like day and night (and it was). Your eyes will adjust for the lack of light if you commute at night.
Now when I ride at night, and I have habit of using three headlights. The first is my main light, a generator light from Schmidt. I like it, it provide a good light and I never have to worry about the battery. Schmidt produces three types of Generators. The first is a HUB generator called the "Son". The Generator literally replaces your front hub. It costs the most but I have had no problems with it. Schmidt claims it is just a little more drag than an XTR front hub, but I have had both and I can not tell the difference.
Next on the list is Schmidt's is their barrel generator generator which you turn off and on by pulling it off your tire. The third generator is a cheaper version of their barrel Generator. It is cheaper but causes more drag when you are pedaling. One word of caution, do NOT get one of those cheap generator from your local Walmart type store. They tend to tear up your tires AND the drag will turn you off generator lights forever. All of the Schmidt's generators have way less drag than those store bought generators (Which I admit I used as a youth and found to be NOT worth what I paid for them).
The next set of lights I use is a converted headlamp with five LCD lamps. It is not bright, but give me a decent backup as a head lamp on my helmet. I also have a AA flashlight that I mount on by handlebars as a back up, gives adequate light in a pinch but strictly for backup.
The third light I use is a Nite Rider HID head light. It fits on my helmet. Like the Schmidt it is expensive but unlike the Schmidt very bright. I tend to use it as a high beam i.e. only used when I need extra light over and above what the Schmidt SON gives me. The chief problem with the HID light (and all battery lights) is that the Batteries tend to last only about 3-4 hours (less if the temperatures is less than freezing which is often the case in my area).
I use the headlight lamp for it frees up my handlebars for other junk (Including my hands). The battery I either keep in a pocket, or in a bag on the bike or when I am willing to carry the weight on the helmet (It really weighs down the helmet so most people will dislike it in that position). Now How I attached the battery to the helmet is first I attached a Velcro system to the Battery and the Helmet. I than strap th battery in with a Velcro strap (You need BOTH for the battery to stay on the helmet, either one by themselves will fail, but together the battery pack will stay on the helmet, but again the helmet will be quite heavy and most people will opt to carry the battery in a pocket).
One of the great things about a helmet lamp is that your light will go where you are looking NOT where the bike is going. When used with another light on the bike this is a good combination (One light lighting where the bike is going, the other light lighting up where you are looking). Remember where you are looking and where the bike is going may be two different places (through most times will be the same).
Note on rechargeable lights and battery lights. Rechargeable lights are the brightest lights and the cheapest to operate (excluding the Generator lights). The problem is once the battery pack is dead you have to charge it or replace it with another battery pack (You just can not go into a store and buy a battery for it). Battery lights are good, if you use rechargeable batteries, as cheap as a rechargeable light AND you can go into any store and buy a battery when you need it, but tend not to be as bright as the Rechargeable lights. I keep one battery lights as a back up to my main lights (Through to be honest I have NEVER had to fall back on them and hopefully never will).
As to the lights themselves, I have been going more and more to LCD lights. While not as bright other lights, you do not have to worry about the light burning out. Thus I would go with a LCD lights in most circumstances. Now for my Schmidt I started out with Halogen lights and than converted to Schmidt's new LCD light. I could see no difference in the area lite (Most of the newer LCD lights use bigger LCDs and magnifiers to max the light outputs). Again neither set of lights were as bright as my Nite Rider HID light.
Now most states do NOT require tail lights when a bicycle is used at night (Through most states require a headlight). While not required I would recommend a tail lights. These went LCD over ten years ago for LCD provide a very good marking type light with very little power drain (i.e. if battery operated can last up to a month of use when only turned on when it gets dark). If you go with the Schmidt Son I recommend a tail light with the Schmidt, but I also recommend a second rear light just in case. Now the Nite Rider has an option of a taillight which I put on my helmet. Gives me a third set of tail lights.
For more on the Schmidt's Son see Peter Whites Wheels:
http://www.peterwhitecycles.com/For more on the Nite Rider Lights:
http://www.niterider.com/products.php?sku=6396Nashbar has a attachment device for attaching a AA flashlight to your handle bar:
http://www.nashbar.com/profile.cfm?category=101&subcategory=1065&brand=&sku=3203&storetype=&estoreid=&pagename=