I don't find any of the buttons on the Steam controller difficult to use or reach. In fact, one thing that surprised me most after receiving it is how it immediately felt better and more comfortable to hold to me than pretty much any dual analog controller I ever used (and that includes all the DS'es, the XB pads, most any Nintendo controller, and at least 3 different PC third party controllers). In particular, it's the only controller where I can put different finders on each of the shoulder buttons (and in this case, the grip button) and have it feel completely natural.
It's almost a meme at this point, but I have to think that with the vastly divergent reactions to the Steam controller some people are holding it
wrong. For the record, this is how I hold it: (note how everything is easily reachable without changing my grip even with my puny little hands
)