i also use a cygolite. not the z-force, the model escapes me now. i really love the quality lighting. my pro's and con's are the same as yours are.
i just returned my light because one of the on/off switches wouldn't catch. i called cygolite, and the guy who answered the phone says 'dude, just take some needlenose pliers and bend the metal contact' >> i couldn't believe it. i did it and screwed it up even more. i just sent the unit back to them so they could fix it.
I'll follow up when i see the result of this fix. (unit was used for one full season)
my only complaint is that they do not make a wider mount, so if you run the newer thicker handlebars (road) it doesn't fit. i have thin bars, but my buddy has wider bars and had to rig it with heavy gauge wire to make it clamp around the bar.
my unit has the water bottle style battery. i have the low light indicator on the light itself, and it is useful.
I need it for ~ 40 minutes during early morning rides in the spring and fall, so i can get many rides out of a single charge.