It could be more like photoshop, where if you expand the icons, it also shows text. Clicking on the icons expands the panel (docker). This makes multi-column dockers rather convenient, since you can collapse the whole column to a bunch of icons, so you don’t need to rearrange all of them when you want to have the second column again.
As for vertical tabs, I think that icons on the sides require more screen real estate then horizontal. Or at least I find horizontal less intrusive, since there is less blank space. Though as I said for collapsable dockers, the way Photoshop does, then vertical makes sense. For expanded dockers, horizontal please.