Since the first beta, which was released less than 4 weeks ago, 1665 bugs new bugs have been opened, and 2243 bugs have been closed. Since the release of KDE 4.1.0, more than ten thousand bugs were closed, showing a massive focus on stability in the upcoming KDE 4.2.0 which will be released in January 2009, 6 months after KDE 4.1.
Полный список изменений в анонсе по ссылке: kde.org