nnBackup 2.28 b8 is available for download.
http://www.nncron.ru/download/nnbackup228b8.exe
This is a bugfix build. As far as I understrand we can expect a stable nnBackup release soon.
Don't forget to take a look into history.txt! All the new features are described in online docs: http://www.nncron.ru/nnbackup/help/help.htm .