ARMS is legit, brehs. Spent some time going through the grand prix mode and playing some online. Initially I got destroyed by the CPU on level 4, so I tried it on level 2, got a feel for things and unlocked some new gear, then went back and beat level 4 to unlock ranked matches. I wish that party mode wasn't random and let you choose which modes you want to play in (not a fan of 2v2), but apart from that, no real complaints. The net code is solid and you don't need perfect execution in a game like this anyway.
They did a good job of making their own version of Gundam Vs. Gundam a different type of fighting game. The focus is on positioning/movement and using the right type of ARMS, not on high execution and combos.
I wonder if ARM weapon balance will be an issue, though. It kind of reminds me of CoD in that newer players are going to struggle a bit against people who have more ARM types unlocked when they first start playing.