I haven't played with it yet...But I've put about a thousand rounds through it on a range, had a fiddle inside, downgraded the spring etc.
Aesthetically, beautiful. It looks mean and the materials used in its creation are of clear quality.
It also feels nice, even if you're not pulling the trigger, it's got weight and a good texture, as well as balance. If you're firing it, there's a definite lurch in the gun when the bolt moves; it's not quite 9mm, but you feel it and it makes the experience worth having.
Sounds mean too, there's a hefty blowback and the gearbox sounds healthy.
Range is 30-40m out the box with just a 350fps downgrade, hop makes a huge difference; without hop the fps is erratic, with a little hop it'll sit within about 6fps range.
Overall, Finius is a happy camper.