I looked at a lot of options, and settled on the Bush & Muller Ixon IQ. A HUGE thanks to Peter White Cycles' website, where there is a great amount of information about various lighting systems. You can read a lot of information about the light on PWC, but I'll tell you why I bought it.
1) Runtime. 4-5 Hours on high, 20 hours on low setting.
2) Great optics. It's bright.
3) Rechargable AA batteries - this was the clincher for me. The light comes with 4 NiMH AA batteries, which are both easily replaceable AND rechargable WITHOUT TAKING THEM OUT OF THE LIGHT.
I just got my light today, and so far I am pretty happy. The mounting system was really easy to use, and I got a spare mount for the icebike for about $3 that will make my life easier. The mount isn't super tight on the 25.4mm bars on the icebike, so I will probably wrap the bars with a bit of old tube to make it tighter.
The only thing that is a little akward is that the plug-in for the charger is on the bottom of the light. They did that so it would be more water-resistant in the rain. It is accessible on the mount, just a little bit more difficult.
First ride tomorrow, it won't be super dark but enough to get a feel for the light.
Some pics of the light mounted below. You can see that it's pretty small, no separate battery pack, no cords!
Here's the light in the garage with no other lights on:
