A lot of people say that the new design is for kids, it's "Fisher Price" (going back to the same term used when Windows XP first launched), it isn't serious enough and looks like crap.
It's not 'twee' to me. It's not Fisher Price. It's akihabara and Vegas. It's bold, brash, American, neon, digital, masculine. It's true that they didn't go skeumorphic. There is no car interior that looks this digital. There are very few home interiors that look like this. It's about media, very tech magazine-ish. And the colors don't match.
Now, before I continue, let me say I'm among the few that like Metro as a desktop improvement. Finally they fixed notifications, widgets and online integration. Perhaps in time my need for chrome will fade away, who knows? Certainly it's easier to recommend to family members.
But talking purely aesthetically, there's a proportion of the non-techy world that is female and I'm guessing won't like this. It's like Media Center, which was also savagely off-putting.
Just look at it for a second. What does it remind you of? Bricks. Legos. Banner ads. A crazy quilt, perhaps. Anecdotally, by the way, Lego has had to re-design, re-brand and re-package LEGOs to appeal to girls. So I think there might be a gender disconnect here.
It's functionally better, but I think that aesthetics will influence sales. Particularly business sales. And it's so subjective, while it might matter, I'm not predicting rejection or revulsion or anything specific. But I think MS, like certain car makers, skews masculine at times and I think Metro shows this more than the traditional desktop that was less in your face and less geometric, where you'd see a wallpaper of a green field (and yes I know the desktop is still there). Not that necessarily women have any problem with LEGOs or geometry or bricks, but statistically they seems to find those less appealing, again, afaict, imo and ymmv and all that, not meaning to caricature the female gender or paint with broad strokes, we're all different after all.
Also, we can take a peek at Android to see how "male design" has influenced sales: it also skews masculine due to Verizon's Droid ads and Google culture, but seems to be doing pretty well for himself, especially considering the ICS redesign which, as Metro, gets rid of most skeumorphism in favour of lines and strong colours and typography.
Back to Metro, perhaps they need a live tile with, "Don't Panic," written in large friendly letters. But the truth is that nothing stops you from having a start screen that is visually made up mostly of pictures of your friends & family which shows their latest messages & updates.