5 or 6 missions in and I'd say it's decent. Decent mission variety (puzzles, fun with physics, enemy types, stealth sections, escapes, platforming, etc.), nothing too intense aside form some space pirate gangbangs. I'm having fun, wanting to play more. I just wish it was on a console with a different art style. This could be Destiny with Prime gameplay.
The saddest thing about this game's probable failure isn't that it's going to destroy the Metroid franchise (it won't), but that we may never see a Federation Force type game on consoles. It's got potential to be a great sub franchise.
Right now I'm calling it a 6 or a 7, with 5 actually being average. It's just a slight hair above average. But it's growing on me so I may end up liking it more as I continue to play.
And I know Blast Ball ain't got shit on Rocket League, but honestly, it's about the most fun I've had with a tutorial mode ever.