I don´t know about any bugs in N6 since I didn´t upgrade. I was severly disappointed that the visibility features in the arrange window didn´t make it to N6.0 , but N6.5 will be a day1 purchase.
So far N5.5 works great for me but I want those features shown for Cubase 7.5 as soon as possible.
One thing left to ask, will there be improvements for window handling?