In my personal opinion they could all be removed and replaced by 'collapse all'. (and perhaps 'expand all')
Another opinion / personal preference - a few Programs I use that deal with nested hierarchies have adopted Shift & Left Click on the Groups/Nodes 'triangle' bit, to expand / collapse the whole hierarchy underneath, which I am a fan of in terms of simplicity / de-clutter all at once... but, it is yet another interaction model...
But, having a way to expand/collapse is neat already! (I have yet to upgrade & try it though...
Just my few centimes.