This may have re-occurred in Vivid.
I just installed 15.04 x64 Desktop, using Nemo in Compact View when just hovering in the directory using the scroll wheel up is right and down is left. This is the reverse of the scroll wheel behaviour in 14.04.
When the mouse is hovered over the scroll bar in Nemo the scroll wheel behaviour is correct (up goes right, down goes left).
I also tested on the scroll bar in Synaptic and found on the non-Unity scroll bar the horizontal direction is reversed.
This may have re-occurred in Vivid.
I just installed 15.04 x64 Desktop, using Nemo in Compact View when just hovering in the directory using the scroll wheel up is right and down is left. This is the reverse of the scroll wheel behaviour in 14.04.
When the mouse is hovered over the scroll bar in Nemo the scroll wheel behaviour is correct (up goes right, down goes left).
I also tested on the scroll bar in Synaptic and found on the non-Unity scroll bar the horizontal direction is reversed.