I'm using Ubuntu 14.10, unity, x64. Also have an nVIDIA GPU (Optimus 555M) if that's at all relevant for this issue.
I'm not sure if I'm missing anything, but I cannot seem to reliably change the theme - if I use unity-tweal-tool, gnome-tweak-tool or ubuntu-tweak, none work.
None of the following change the theme in either tool:
Selecting a theme
Double clicking a theme
unity --replace after changing a theme
compiz --replace after changing a theme
The only way I can seem to change theme is to select a new theme, close unity-tweak-tool, re-open unity-tweak-tool, if the theme option has stuck with the one I've selected reboot the computer - if not re-select it and repeat til it sticks, then reboot.
To my knowledge, just selecting a theme in either tool should auto apply it so I'm not sure what I'm doing wrong - any ideas?
Edit: So I changed the environment to Cinnamon and I can change themes there - so it seems to be something to do with Unity I guess?