Well yesterday I decided to go ahead and get the Dual Cross Pro Li-Ion at the LBS nearby. I read some very positive reviews of it and I came out of Christmas with more money than I thought I would have.
Here are some comparison shots. Please note that my camera's sensor is not as sensitive as a person's eyes, so both lights appear to be much dimmer than they actually are. The first is my Cateye EL 520. It has good runtime on four AA batteries, but it is far too dim for my commute in rural Missouri. The light swath is also much too narrow. I will probably be moving it up to my helmet.
This is the Cygolite. Given the overall better brightness and huge lit area in comparison to the Cateye, I'd say this light gives off around 12-15 times the light of the Cateye. It's incredibly bright (especially when I accidentally look into it) and the light swath will be much more usable on my commute. I will be able to see to the sides a little to avoid road hazards, and it lets me see much farther down the road.
Runtime is advertised at 3.5 hours on high or 7 hours on medium. Medium brightness looks only slightly dimmer than high, so I could likely use this to ride long into the night if I need to.
The battery is tiny and weighs only a few ounces. I have it mounted on my stem. The clamp for the light is quick-release so I can take it in with me when I go to work, and it doesn't shake or move around as much as the one for the Cateye.
Overall I'm very impressed with the unit. I was originally considering a Dinotte 600L, but now I feel that would just be overkill and a waste of money for my uses.