When I take new buyer clients out to view homes, while we're driving around in my car and getting to know each other, I tell them that among other things, there is one very, very important rule that I have: They must be honest with me!
I tell my buyers right up front that I will not be offended if they don't like a home's floorplan, or the wall-after-wall of wallpaper, or the Pepto-Bismol-pink bathroom. (I had one of those in my first house...) After all, I'm not the one who chose those pink bath tiles.
By telling me all they like or dislike about each home we view, I then learn more about their wants and needs in a new home - and what issues they can and cannot accept in a home - and I am then better able to choose and decide which other houses might be a good fit for them. It saves us all a lot of time if I know they can't fathom the thought of removing wallpaper (I hate doing so myself) and I can then eliminate those homes where wallpaper is in use as if it were going out of style (and it did!).
Communication is key between buyers and their real estate agents. Talk openly. Be honest. Be blunt. I won't be offended, but I will be better able to find your new home!