An anonymous reader writes: Today Microsoft officially released Windows 10 in 190 countries as a free upgrade for anyone with Windows 7 or later. Major features include Continuum (which brings back the start menu and lets you switch between a keyboard/mouse UI and a touch UI without forcing you into one or the other), the Cortana digital assistant, the Edge browser, virtual desktops, DirectX 12 support, universal apps, an Xbox app, and security improvements. Reviews of the operating system generally consider it an improvement over Windows 8.1, despite launch-day bugs. Peter Bright writes, "Windows 8 felt unfinished, but it was an unfinished thought. ... Windows 10 feels unfinished, but in a different way. The concept of the operating system is a great deal better than its predecessor. It's better in fact than all of its predecessors. ... For all my gripes, it's the right idea, and it's implemented in more or less the right way. But I think it's also buggier than Windows 8.1, 8, 7, or Vista were on their respective launch days." Tom Warren draws similar conclusions: "During my testing on a variety of hardware, I've run into a lot of bugs and issues — even with the version that will be released to consumers on launch day. ... Everything about Windows 10 feels like a new approach for Microsoft, and I'm confident these early bugs and issues will be addressed fairly quickly."