Microsoft on Wednesday announced Windows 10 is officially available in 190 countries as a free upgrade for Windows 7/ 8/ 8.1 users and new PC and tablet users. The company had opened a reservation system earlier this month, and will be rolling out the upgrade in waves.The Redmond giant has a lot riding on this release, with the aim of patching up its ecosystem after the consumer reaction to Windows 8. Microsoft is clearing trying to bring the best features from both Windows 7 and Windows 8 to its latest offering, and does provide some tempting features for an upgrade. However, Windows 10 also clearly appears to be a work in progress, with several bugs and issues remaining. Users upgrading from Windows 7 and Windows 8 will also lose some features.