The gradient window bug seems to be rather old I suppose. The color bar slides when it shouldn't. If this is a feature, it's not very useful. It's OK to be able to slide the colors to pick a better gradient position (quite obvious), but not when it's not wanted (i.e. ALL the time).
The addition of this new "preview" pane is making the program crash more than usual. If you try to do something very fast and the preview pane hasn't rendered all the samples (of a new batch), it crashes. Badly. The pane could have an option to be turned off.