I used the Finn in WZ last night, though I haven't levelled it up much yet so I've definitely not unlocked its potential. Still, it was good but I don't get the hype, felt like a slow GRAU (pre-nerf) but with more bullets.
It's funny though, always when a gun is called overpowered, I decide to use it, but then end up going back to the m4a1 cause I just get way more kills with it, happened with the GRAU and will probably happen with this too. I dunno, just feels like there is no better assult rifle at a mix of short and mid range, and I wasn't good enough with the GRAU to unleash its full potential at mid-long range with the default sights anyway.