This is what Windows 8.1 looks like without tile gradients.

Here is a quick mock up to show what the Windows 8.1 start screen looks like without tile gradients.

Imldtpe_medium

and here's what it looks like now.

Bxhkqgy_medium

Granted, it's subtle. You can see the difference a little more easily by viewing this gif (click to enlarge/start the gif)

Onsr4o_medium

or by going to the imgur link below and switching between the two pictures. The imgur link is obviously a lot higher quality.

http://imgur.com/iMlDTpe,BxHKqGy#0

Personally, I really prefer no gradients, as I don't think it's very metro at all.