This release is a major improvement in the 5.X series, which includes a large number of new features and bug fixes.

Some of the key new features include: namespaces, late static binding, closures, optional garbage collection for cyclic references, new extensions (like ext/phar, ext/intl and ext/fileinfo), over 140 bug fixes and much more.

We have confirmed the date with Microsoft, and have received this helpful definition: “General Availability (GA) is when consumers can actually purchase the software and PCs with the software preinstalled.” Also, “release to manufacturing” (RTM), when the finished software is given to computer makers to pre-load on new machines, takes place in “late July,” presumably over a matter of weeks.

http://gizmodo.com/5275938/windows-7-to-be-released-october-22

Microsoft has confirmed it! Ars has more at http://arstechnica.com/microsoft/news/2009/06/windows-7-arrives-on-october-22.ars

Windows 7 is the operating system that I am using right now and I would say that it is really stable.