Sigh. Literally my one complaint about Windows 8 was the fact they forced me to get rid of my beautiful Aero glass and replaced it some extremely flat, very plain look. Flat shapes. Squares mostly. So.. what does Apple go and do? Gets rid of THEIR very detailed, graphical and elegant look and replace it with-- guess what-- MORE FLAT colors and shapes. Oh, but they have gradients.
I always hated gradients when used this way though. The same kinda gradients that's normally used in very amateurish looking UI skins or apps (a lot of the windows 8 third party apps do this too, drives me nuts). What I'm talking about is when you take a simple shape, and just floodfill a standard gradient. That's it. No contour shadowing or highlights, nothing dynamic, nothing even remotely trying to render any sort of depth. Just a gradient. Apple got rid of all the polish and is trying to copy the very move that MS made that I hated. Sure, it's colorful, but the colors used don't even work real well together and it just looks like a gradiented rainbow nightmare. There's no longer any consistency or order, just flat gradiented color chaos.
I'm completely against this trend where 'everything is flat'. I hate flat. I never wanted flat. I want my aero glass and well shaded and glossy artwork. Flat is just being lazy. Anyone can make a UI out of flood-filled rectangles and circles. A 5 year old in mspaint could do that. That's not how sloppy I want my UIs looking on every damn device I come across. I want back my elegance, but it looks like elegance is gone forever, replaced by flat flat flat.
As a windows 8 user, I'm STILL waiting for a way to bring my Aero glass back (without some broken or annoying nagging software that attempts at doing so).
Now, I didn't mention Android. I personally never found Android's UI to be particularly good looking, especially since everything (especially the iconography) seemed completely inconsistent and rushed. However, even among Android devices there's an awful lot of flat showing up. Especially on the manufacturer-specific homescreen replacements, like htc sense and samsung touchwiz. Somehow, though, they manage to make it look nicer than either the Apple iOS7 or "Modern" MS offerings.
I want pretty UIs, it's a shame that I'm no longer ever going to be able to enjoy this preference anymore unless I go back to using older operating software.