I can drag any .desktop file to the launcher, which is great, but where to put a .desktop file for it to appear in Unity's dash and dash searches? Apparently not in /usr/share/applications.
The apps place has a ~5s gracetime before it indexes new apps. They are indeed picked up from
/usr/share/applications (among other places). I just tested here and it seems to work fine.
Right now you have to do a search or something else to change the result set though - it's only the underlying index which is updated right now. For this Thurday's release I'll land a fix so that we also update any active result sets when we detect changes.