First impressions on the new P20, it does indeed feel like it has been built for combat. It has a very stout feel. It's shorter than even the P12, so it sits very tightly in your hand when your fists are closed. It's light weight, so it doesn't hamper your movements. The larger diameter head gives you stopping grip when you're striking, so it doesn't slip out of your hand.
No rattling or shaking from this light. Everything is rock solid and compacted. The best part comes in the form of the Strobe-ready tailcap switch. It's essentially a super easy access strobe switch that you can activate even when you're wearing gloves or mashing it in distress. There's no SOS or beacon blink modes, but that's fine as it was built for combat and defense use. The beam throw is medium range with wide spread, excellent blinding power within 50 meters.
Interface wise, there are 3 modes, Military (Turbo / Strobe only), Law enforcement (Turbo / Low / Strobe ) and General (Turbo / Medium / Low / Strobe). So just choose your preferred mode of use and you're set. The crenulated bezels are an effective glass breaker and WILL HURT when struck on soft skin and bone. But not to worry it is still safe to carry on board planes.
Highly, highly recommended for all duty personnel and civilians that want something more than just an illumination tool.
You can get the P20 online here - http://www.nitecorelights.com/products/p20-800-lumens