Yeah, I have the Marushin Ruger.
It's basically bulletproof.
I doubt KJW exactly went back to the drawing board on this one, so it's probably almost identical to the Marushin. (Seeing as the Marushin was released, became very popular overseas, and then KJW releases one...)
400+ fps is not unreasonable out of this gun, but don't expect it past the first 4 shots. And don't expect to get real efficient gas use. The gas tank is small and it uses a LOT of gas. Essentially the design of the Marushin has the barrel being pulled back to grab the BB from the magazine, where it mates with a small piece of barrel built into the mag just forward of the valve. Gas goes straight from the mag through the barrel to shoot the BB. Brutally effective, simple, and inefficient.
The other thing is that while you will have high velocities, a 5 inch barrel equates to a lot of flyers. Accuracy is great, when you're sitting down calmly plinking. Anything that affects gas performance really affects this gun. Hop up is pretty good, but keep it adjusted well.
And the final thing is that this is not a very good combat sidearm. The trigger pull is just too long to get of successive shots fast enough.
That all said, I love mine.