I certainly like both Cadance and Shining Armor. For characters who could have easily been made milquetoast stock personalities, no more than necessary stand-ins to facilitate the events of "A Canterlot Wedding", the writers have provided both of them with unique traits which are consistent with the rest of the cast. In other words, Cadance and Shining are relatable as people, even if they occupy prestigious positions in society. The two of them take most everything in stride with a pinch of good humor.
Cadance possesses an air of refinement without being a pompous Mary Sue who chews up the scenery and minimizes the importance of other characters. It's clear that she knows she is a princess, but she doesn't let her status contort her personality. I wish I could put my finger on it, but there is something about Cadance that leads me to believe she is not perfect---even if she has committed no major blunders thus far in the series. I could easily envision her being very honest about her mistakes and shortcomings.
Shining Armor has a touch of the adorkable hero who is equally capable of leading a squad into battle to defend Equestria and being humorously embarrassed by his little sister. He's really the Captain America/Steve Rogers of MLP. I also think the surfer accent makes him a bit quirky.
I guess people could dislike both of them for being too perfect a couple. I honestly don't get that vibe from them, though.