Canonical is developing new things for Ubuntu 13.10 Saucy Salamander day and night, in order to make it available for the 17th of October.
Until now, the users have to left-click once the shortcuts in Unity Dash, to open the desired applications, and a single right click would open a preview of the app.
After the modifications brought by Canonical in the latest daily builds of Ubuntu Saucy, left-clicking and right-clicking do the same thing, open a preview of the file. The users have to double click the app, in order to open it.
I think they have made this changes, in order to make the users discover the preview feature. We don’t know if this feature remains for the final Ubuntu Saucy, but I hope not. Why to “fix” somethings that does not need to be fixed?