sweeks

I've been using a Vizy for about one year now. I ride 5 days a week, about 7 miles a day, running the light all the time, in all kinds of weather. I charge the light once a week. I've seen no indication that the light's battery is wearing out. It's a Li-ion battery and is, as you noted, not replaceable. Battery technology has gotten pretty good recently (read: "Li-ion"). When the battery *does* eventually fail, the unit should be recycled appropriately, not discarded in the trash. Likewise, if you use a light with replaceable batteries, you'll have to dispose of them somehow. Modern alkaline cells (eg: AA, AAA, etc) are OK to put in the trash in most areas, but you'd be throwing a lot of them away during the same time period as the life of the Vizy. You could of course use rechargeable cells, which require appropriate disposal as well. Personally, I have found the performance of the light quite satisfactory, and the freedom from replacement and disposal of batteries very convenient.

I should note that the circle of light on the pavement doesn't show up terribly well when there is ambient light, but when you are in a dark area it's pretty obvious. There is a rear-facing array of LEDs that is quite bright. It's not as bright as the Dinotte 300R rear light I had been using (brightest rear light I've ever seen), but I can see its light reflected by stop signs 100 yards or more behind me. The only complaint I have is that the various flashing modes do not include one with the down-facing LED *off* since it doesn't contribute much in the daytime. Since I only have to recharge once a week anyway, this is not an issue.
Steve