The NiteRider MiNewt sucks. Sure it is small, comapct, and Lithium Ion, but it doesn't compare to a standard 10watt. I would spend your money on a Niterider Trailrat, or a Sigma EvoX. Really, dollar for dollar, the Sigma Evo X is the way to go. The Niterider MiNewt is cool, and the light colour is cool, but the light throw just isn't as good as a nice 10 watt halogen bulb. If you want LED, pony up the extra $$$ and get a Cateye DoubleShot. That is a light! The DoubleShot gives you 5 hours of run time out of a 3 hour charge, and is an awesome light for XC. The only downside of the doubleshot is that it only has 2 settings, off and on. I heard there is a new DoubleShot Pro coming out that will have a high and low setting, and even more light output, but is going to be HID priced.
LED is the wave of the future, the MiNewt is a dissappointing first attempt by NR though. If you are considering a MiNewt, just save some money and get a good 10 watt halogen system.