I don't agree with flat Metro UI, even when some of the big products (from Microsoft) forcibly using it. It is something that should be only on Microsoft's failed Windows RT platform, where normal desktop applications can't exist.
Now major flaws in new ManicTime Metro UI:
1. Inconsistent UI. Some of the controls are default Windows controls (Windows, CheckBoxes, RadioButtons, ComboBoxes, ScrollBars) and rest of controls are custom themed.
There are tiny controls that can be easily overlooked and are undistinguished (Settings and Info). It is not clear what tab is selected on first look on custom themed TabControl.
2. Clock logo have no function, it is too big and very distracting.
3. Wasted vertical space by StatusBar and Filter on two rows. Gray gap between timelines and lists is also wasted vertical space. Keep in mind that lot of users have widescreens with pitiful vertical space.
4. Black text on dark blue background is unreadable.
User interface in versions 2.x was clean, intuitive and good looking.