I just finished the first cup (Cobalt). The scoreboard says that there are at least 17 200 other people that has done it too.
This a super cheap racing game - approximately a third of the price of an AAA game like F-Zero/Wipout. It probably will not sell a lot more than 100 000 copies.
Nintendo is watching this and deciding the fate of future F-Zero games from the sales of FAST Racing NEO.

On a scale from Double Dash's Baby Park to any F - Zero GX stage beyond the third cup, how hard is this game?

GX first three cups hard.

Just got the game. I've only done a couple races so far. My WiiU locked up on the first attempt, hard reboot fixed it. Initial impression, good attempt. It doesn't look as good as Wipeout HD and I miss first person view and air brakes but the color switching mechanic is nice and Wipeout is dead. Beggers can't be choosers.

I do hope they patch in first person view at some point. I miss the screen tilting in the corners, makes it all a bit less exciting. It will probably get better in the faster racing cups.

The game is fantastic, ive had no problems with online, no freezing and has been running smooth.

So, anybody managed to get up to Hypersonic yet?

I'm still practising on Subsonic myself. Just played Titanium Cup. Storm Coast took my breath away, absolutely gorgeous.

I've cleared all three leagues, though I haven't gotten first in all cups.  Right now I have all gold in Subsonic; two silvers, a bronze, and a gold in Supersonic; and one gold, two bronzes, and a silver in Hypersonic.  I have also beaten 8 of the courses in Hero Mode (which I actually find easier than the straight Hypersonic league since the AI doesn't compensate two well with the shield mechanics).  It took me a bit to get used to the controls but I eventually settled on a set of vehicles I was comfortable with.

I will say that I absolutely loathe with extreme passion the course Sunahara Desert.  There has never been in any game any course or level I hate to the level I hate Sunahara Desert.  That course is the reason I don't have a gold in that one cup in Supersonic.

But one thing that blows me away in Hypersonic is the absolutely INSANE sense of speed.  It's just crazy.

I've been putting that game on hold for far too long now, was also trying to get platinum for that back in the years it released... But I'm warming up with wipeout 2097 :)

Splatoon was #1 in the German eShop charts for months and is dethroned by FRN now.

You probably know this, but you should use Time Trial to figure out how to drive Sunahara. Use ZL and ZR on the sharp curves and maybe even brake sometimes. Use boost when going out of curves. Or you could even try to use motion control - it only kicks in when you move the controller.

I am still on Subsonic, due to lack of time,  so I am maybe not the best to give you hints on how to win though!