I am sure there is "room for improvement", like anything. Nor am I saying it is the "end all" of pre-amps. I am sure there are those who might listen and prefer another pre in a host of different contexts and systems.
My comments were merely a comparative opinion as a Ref 3 owner. In that context no, I did not notice any downside to the Ref 5, it was better in all respects in the areas I mentioned and others. As well, the cosmetics are improved with the matching brushed "natural" anodized handles.
My "different ends of the line" comment was a means of qualifying the improvements between the two units as estimable. Overall there was noting "solid-state" like with the Ref 5 other than its tight pitch articulation, background silence and a perception of improved extension at frequency extremes. My apologies if that was not made clear.