I commute with a Niterider Blowtorch, and a Light & Motion Vega as a back-up light and forward facing blinker.
The brightness and pattern data here is pretty much dead on if you haven't seen this link.
eddys.compage.cfmOpen ↗
I would definitely say that the HID lights are worth the money. A good one will bath the road in enough light that you can pick up and avoide glass in the road even at daytime riding speed. They get you noticed too. Most people who see me approaching at night think that I'm a motorcycle. On dreary days when I use it for the commute leg home, I get lots of people who just stare or ask me at a stop what kind of light I am using. So I know that they can definitely see me.
The main thing that I would say that I have learned is that you can save some money by shopping for a light based upon required run time. I can basically get the same HID light in terms of brightness and watt rating but with a smaller battery capacity for a lot less money. Another element to cost is the type of battery that you will be getting, as well as the type of charger, i.e. fast charge and automatic being the higher end.
Just do your home work and decide what best fits you. There are plenty of good deals out there (in the states) now that daylight savings time has shifted.
Personally, I have been much much much more impressed with the L&M products than with the Niterider. My system is holding up only a little bit better than did Hincapie's PR fork. And so far, using Niterider's tech support has been pretty disappointing. My system is still running after two full years of commuting use and abuse, but mostly because I have been able to trouble shoot it on my own. Simply put, I don't think that anybody else could even walk up to it and get it to work, it is that quirky after being out on the road and in the wet. The L&M stuff has held up much better and appears to have been made with simpler designs and components.
Results vary of course. Hope this helps. 😉