My floor pump came with the old head, which was always iffy from the get go, but just suddenly stopped sealing one day after frankly not that much use. This one ... at least it's not a guessing game of did I get it on right, but the first tube I tried it on, it doesn't work with. For some reason. All my other tube stems work great, but the one on my rear trainer tire, it's like it doesn't screw down quite far enough or something and the stem valve never opens. Oh well. At least it works most of the time.
I run a Garmin Varia radar taillight, which is great except its daytime flash is 65 lumens, not that bright. So I got this for its as a second, brighter taillight: 300 lumens daytime flash with a 5 hr lifetime (or 150 lumens for 7hr). This unit works beautifully, and, given its 11 (!) modes, it's really helpful that it "remembers" the mode it was last in when you turn it on again, so you don't have to click through all those modes.
One improvement would be for Lezyne to bevel the light's rubber mount so that the light would sit nearly vertical on a seatpost instead of shining slightly downwards. Most seat posts lean towards the rear, the mount should be redesigned to compensate for a "typical" seatpost lean.
I ride only in the daytime, bought this for its 1000 lumen daytime flash mode and 7.5hr lifetime in that mode. Very bright and its flash sequence is definitely attention-grabbing. Given that it has 8 modes, it's great that it "remembers" the mode you last used last. When you head out for your next ride, you simply hold down the power button until the light turns on, about 2 sec. When you finish, just hold down the button again until the light turns off - easy.
A few niggles:
(1) gotta pull hard to fix its rubber strap around the handlebar, helps to rotate the light 45-90 degrees on its mount
(2) to avoid reflections off the screen of my Garmin (on its "out front" mount), had to mount the light upside down below the handlebar, putting the power button underneath the light where I can't see its state of charge indication - move the power button to the rear of the unit (or have dual power buttons, top and bottom?)
There are loads of these lights. I picked this one because of it's relative brightness. I immediately noticed motorists noticing me more often. The light has several settings but if you are riding during the day the high intensity flashing setting is really the best option. The rubber band is a bit of a struggle to take on an off the handle bar but once secured doesn't show any sign of wanting to depart the bike. Charging the unit is also easy relative to other tech since the light plugs directly into one of those cubes. You don't have that annoying search for which cord to use. How long does it stay charged? I have gone on 3-4 hour rides and still had light. I am trying to charge it every other ride just as a precaution. You can press the "on and off" top button to get an idea of how much juice is left. In all respects I am happier with this light than my much larger ,heavier and harder to secure Nite Rider.