My thoughts are that going too heavy into iillithid use will lock you into a particular route, where as other routes will only really be options if you resist the urge to indulge in the power it grants.
Certain companions, equipment, and potentially styles of play COULD be locked behind not going overboard with it.
But... as it stands, all we know for sure is- if you want these cool powers, you need to make yourself more illithid.
