I love Zebras. They have great size, ergonomics, UI, drivers, and heatsinking. But that said, they do seem to have quality control issues. I've purchased 17 Zebras over the years, and 10 of them have had problems, 8 of which were big enough to seriously detract or destroy the usefulness of the light.
This is a larger failure rate than I've experienced from any manufacturer and makes me hesitant to really depend on my Zebras. I don't really feel comfortable carrying around a Zebra until I've used it for quite awhile and can verify it's not one of the quirky ones.
Here's what I experienced:
SC51 - no problems
SC52 (first run first run preorder) - no problems
SC52w (first run preorder) - turbo supposed to last 1 minute, but typically only lasts 20 seconds even on a fresh high-quality cell. This seriously diminishes the usefulness of the light.
SC62d (first run preorder) - no real problems. Anodizing wasn't quite even, but I don't consider this a defect since in operation the light works fine.
SC62w (first run preorder) - won't stay in turbo for more than 10 seconds even on a fresh cell.
SC63w number 1 (first run preorder) - initially worked fine, but after a couple weeks of light use won't stay in turbo for more than a few seconds. Returned and replaced.
SC63w number 2 - initially worked fine, but after a week of light use won't stay in turbo for more than 10 seconds.
SC80 (first run preorder) - everything works fine except H2 which doesn't work at all.
SC600 (first run preorder) - serious switch problem that caused the switch to activate when just lightly brushed with fingers without depressing the switch at all. This was a known problem with first-run SC600s. Light was returned for warranty repair. Received it 2 months later and it has worked flawlessly ever since.
SC600w III HI (first run preorder) - no problems
SC600 IV Plus (first run preorder) - no problems
H604c - no problems
SC32w (first run preorder) - initially worked fine, but gradually over the course of a couple weeks after purchase the time it would stay in turbo got shorter. After just a few weeks of use, the light won't stay in high for more than 1 second even on a fresh cell. Effectively, the light only has medium and low modes seriously detracting from its usefulness.
SC64w HI number 1 (first run preorder)- when turned on in H1, it occasionally instantly turns off after a second. When that happens the light does not respond to further inputs and the tailcap must be inscrewed to reset it. Problem is occasional. Irritating when it happens, but not common enough to be a big issue. I figure maybe once every 30 activations or so.
SC64w HI number 2 - worked fine for first couple weeks, but then pretty much died. It still reacts to the button, but now won't go above very low no matter what is pressed. Light is unusable.
SC5w (first run preorder) - worked fine for first couple weeks. Then abruptly died. Light still reacts to button presses, but everything is just shifted a lot dimmer. H1 is now about as bright as a bright moonlight and all other modes are dimmer. Light is unusable.
All my Zebras were purchased directly from Zebralight on their website. Most were first run preorders, which could be the cause of my higher than expected failure rate. Preorders don't always have all the kinks worked out. None of them have ever been dropped and except for my H604c, all of them have seen only light use.
I used quality lithium ion cells in all the lights purchased from a reputable dealer (Mountain Electronics), except for the SC5w which used an Eneloop Pro. The problems I experienced weren't due to the cells, which worked fine in many other much higher powered lights from other manufacturers.