I loaded the technical preview as a virtual machine a few days ago. The interface hasn't changed much from Windows 8.1. They turned the start menu into something more like Windows 7... it doesn't open full screen unless you switch into tablet mode, but it still has the customizable live tiles added in. They've included Cortana voice searching into the taskbar (by the start menu button). Cortana can search the internet, but she can also search through all your files on your PC, network locations, Onedrive, etc... plus help you schedule appointments, check you calendar & set reminders/alarms. Basically adding phone features into the PC world.
All those Windows 8 full screen apps now have the option to be windowed & resized like Windows 7 programs. There's a continuum button that switches between tablet & Windows 7 mode. Hybrid tablet/laptops like the Microsoft Surface Pro 3 automatically switch depending on whether you have the keyboard attached or not.
The charms menu seems to be gone & the settings menu seems to have put everything in 1 place... I haven't gone in too deeply here, but it's much better than Windows 8. It's still gonna take some time to learn where everything is.
Plus it's free to upgrade from Windows 7 or 8 for the 1st year (no charge to stay on Windows 10 after that & you'll continue to get all the updates). If you want to upgrade to Windows 10 after the 1st year then you'll need to buy it.
