I have used the Klarus E5 for several months now and while it is annoying in some ways it tends to come in very handy in many situations. Also it is really cheap running typically below 20 USD/EUR. The main problems are visible PWM in the lower modes (not something I would expect from Klarus) and a less than optimal UI/switch solution.
This is my review:
A couple of months back I also (impulsively) bought an E5 on AE, when it was on sale for around € 11,-, thinking “it will be fine, because it’s Klarus” and only afterwards searched here on the forum, where the very noticable PWM was mentioned.
I have tried it out, but the PWM was bothering me too much and because I was probably not going to use it because of that, I have gifted it to my sister, as a handy flashlight for around the house.
Yesterday I recieved my also impulsively bought Klarus HM3 (very small) headlamp and also that one has noticable PWM, although it is a bit higher frequency than the E5, so maybe I can tolerate it.
Luckily it was also very cheap, but I’ve learned my lesson now, in that I have to stop impulsively buying cheap Klarus lights on Aliexpress! 
Yeah, disappointing to get a Klarus and PWM on top of it. I’m very sensitive to flicker of any sort. It does not cause me discomfort but it is distracting. The E5 is really practical and when PWM is not visible on high mode the light is rather beautiful (typical for COB).