I haven't used rhythmbox in a while, but I just upgraded to 14.10 and thought I'd give it a go. I imported some music, playback is fine. I used to use the visualizer and wanted to try it again. I have installed rhythmbox-plugin-visualizer. I've quit and reopened rhythmbox. I've restarted. I am pretty sure I used to find the visualizer option in the view menu, but I can't find it anywhere now (view, tools, or anywhere else). It's activated in the plugins menu. What am I missing? I did see something about it being intentionally left out back in Ubuntu 12.04, but rhythmbox and the visualizer plugin have both been actively developed since then so I am led to believe there must be a way to make it work that I just haven't come across yet?
The visualizer is actually displayed in the left-pane if you have this displayed:
This bit shown at the arrow in the picture only appears when you have started playing any track.
If you have hidden the left pane - redisplay it by pressing F9