Picked up a PA Ultimate Weapon Light Gen3 (FDE) to experiment with and, weight aside, have to admit I'm impressed with the overall quality & ruggedness.
So, until I can hit the range for some night shoots w/this bad boy, what's the consensus of those who already own the Gen3 or Gen2?
Tomac

Little late but, I had one of these a few years back, gen1 or 2 I assume.
It was basically typical Primary Arms, above average for it's origin and price point.
China has been making pretty darn good flashlights for a long time now, it's a
competitive niche market, and it really isn't that hard to make a good flashlight
in 2015.  Despite what Surefire might tell you. :P

That said, it isn't a surefire.  I thought the tapeswitch was flimsy, but the rest
of it was solid enough, the pushbutton seemed ok.  The LED module isn't anything super special but it's reasonable
quality, and they are naturally pretty recoil resistant and such.  As usual, I "wouldn't go to war with it" and all that
but it's a heck of a light for the money if the aged style and size/weight aren't
a bother.  I think I moved on to a G2 LED in a ring mount, wasn't as bright
but was a lot smaller and lighter for similar money.

Thx.
New pic above is what I finally settled on.
By removing the UWL's mount and attaching it directly to the hand guard w/o using a MOE rail, total weight w/the 3-cell setup is 9oz (which, surprisingly, is less than the TRL-1 Long Gun setup I tried before this) and places the switch as close to the hand guard as possible, making it easily accessible to my support hand thumb. By relieving a little material on the hand guard, I could go w/the 2-cell setup at 7.5oz but I'm not sure it'd be worth it to reduce runtime by 50% for only 1.5oz.
Tomac

ETA: Night shoot went very well, I was pleasantly surprised to discover I could hit the 200m gong w/this light, but effective target ID range is less.

They need to make a scout sized version.

Yeah, surprised they haven't with the trend toward smaller lights the last few years.
Arasaka I think it is has a pretty decent semi-cheap Surefire clone I've been eyeing.
Not PA cheap though but it's probly higher quality with the Malkoff head.

I have one of the Gen II lights (420 lumens I believe) on an AR. I really like it. I tested it out by keeping an eye on my dogs at night when I let them out to go to the bathroom. I could easily see both dogs at 300 yards with the light. It is super bright at night and it is not the 750 lumen Gen III. So I would love to do a side by side comparison between them.

Most people do not realize that you can run it as a 3 battery or 2 battery setup. It has a removeable middle section that will make it shorter in overall length and lighter. I run mine as the 2 battery shorter version to cut down weight and make it easier to reach the rear button since it is on a carbine length AR.

I am really tempted to get the Gen III version for Christmas.

Don't wait too long, PA is currently selling them for $65, IIRC (Black Friday):
http://www.primaryarms.com/primary-arms-ultimate-weapon-light-gen-iii/p/kt-pawl-2bkgeniii/
Tomac

I'd be tempted to mount one of these on my plain-jane carbine that has a 16" barrel and a MOE-SL medlength handguard if I could do it without
bolting on a rail section.  I google'd around and don't see a m620 based mount for m-lok.  IWC dosen't seem to even have one.
I'm tempted to order a http://www.impactweaponscomponents.com/product/smcxl-1-light-mount-n-slot/ and
drill the mount to fit the holes on the light.

You can probably duplicate my setup by removing the UWL's mount then picking up a couple of 10-32x1/2" Flat Head Socket Cap Screws and washers from your local Home Depot (Magpul MOE retainer plates drilled out to pass the 10-32 screws might work as well, it's what I did) to attach the UWL directly to your hand guard. See my pic above.
HTH...
Tomac

The size was a bit much for me, but I did buy their compact weapon light for my 5.56 dissipator.  The compact is slightly larger than a Surefire 6P.  If the UWL is anything like their compact weapon lights, it's a winner.  I'm heavily invested in Surefire lights, but I really like the PA compact weapon light.  I'm looking to pick up a second for my 5.45 dissipator if they ever go on sale again.

I've handled them a few times.  I don't care for the size.  Not after running my TLR-1HP.  The HP is very compact and in my field use has shown to have a great long range throw.  

That PA light though is pretty kick ass for sure.  I just can't get past the size.

It's about the size of the go-to Surefire weapon light from years past, just out of date is all.
Ten years from now we'll have a thousand lumen the size if your finger and
call all the pistol lights people use on rifles now huge and bulky. :)