I find the best way to see PWM, aside from a fan, is when walking outdoors. Pan the beam across the grass and defocus your eyes while following the beam, not the grass. A light with PWM will make the grass look like it is digital. It might not make sense until you do it but once you see it you will say "yeah, digital is exactly what it looks like". A light without PWM will leave the grass in the beam spot a blurr.
How about turning on the shower in the dark to detect PWM? That seems always the fool proof way for me. If there’s PWM the lit area of the water is a series of tiny little dots.
It's annoying when you try to take a wall shot, and get nothing but black.
hehe yep 
OK well it’s raining like crazy right now and I can notice PWM on low but not what I would call “bad”. For what that’s worth.
I don’t mind the PWM so much, but I can’t stand PWM whine at all 
It’s like nails on a chalkboard for me, super painful
-Jamie M.
I received mine from fasttech. I must say I am not very happy with this purchase.
First of all, I needed the new srk body style, like in the pictures presented on fasttech site. I received the old battery tube with the straight lines.
The flashlight also came with defective driver board, the leds were flickering and low output level.
The reflector machining looks horrible(see pic)
After taking the light apart, it looks like the driver board is the single toroidal one(see pic). I managed to repair the driver by resoldering one of the 000 value resistor.
Mod report : After repairing the driver, I made a current draw test. With a single trustfire flame it measured ~4 amps.
I changed the wires with thicker ones and soldered a piece of cooper wire over the 0 value resistors. The flashlight is visibly brighter now and the current draw increased to ~5,3 amps on a single TF flame.
I will test again later with 4cells, because it seems that 5,3 amps is the maximum for 1cell.
Please do a review on FT so we know which one to avoid.
Ugh, that’s an awful looking reflector! Wouldn’t be pleased to get one like that
leaftye : It is the flashlight bought from the link in the first post here.
LinusHofmann : exactly !
New tailcap measurement after mod : I was able to hold 2 batteries, the multimeter leads and push the button at the same time 
Current draw ~6,8 A ! Not bad from stock ~4A
I was considering order one of these from Fasttech, but after seeing that reflector I think I’ll hold off. There is no way I’d be happy getting a light in that condition. I guess we are seeing the result of the QC compromises that are being made to reach these crazy low price points.
Hopefully they post it. I have submitted several less than favorable, but honest, reviews on items at FT and none of them have ever been approved or shown up on the product pages. I think if you want it to show up, give it a high star rating and title then write what you really think in the comments section :)