All this cavalier talk reminds me, as someone that prefers martial classes, that cavalier was such a huge letdown in this game. When you can charge, the class is great, but charge is just so limited by unforgiving pathing and bugs. On tabletop you can really fat finger if someone has a valid charge path, but in this game it's cripplingly strict.
After I took a horse for Seelah, some of the complaints about mounted combat became clearer, but some other - way less.
Charging on a horse is extremely satisfying on large open maps, and very frustrating in tight corners. For me it is perfectly reasonable. Bringing a horse into a dungeon or a basement of a normal size house is kind of stupid. Now, if we are to fight in the halls of giants then charging on horses in kitchens and bedrooms would be OK.
As a pure Paladin Seelah does not depend on her horse that much, so in dungeons (which are human-sized so far) I use her on foot and let the horse do its thing. However, anyone who decides to use a class that is efficient only while mounted should think about tight corners, back alleys, house interiors, basements and narrow dungeons. Thus, choose your hero and the pet wisely: the specialized mounted hero has to be a "manlet" and be prepared to fight reduced; and the mount should be small enough to fit with the rider everywhere. Maybe Kitsune are still too big, but there are gnomes and halflings. A Cavalier of the Paw is in the game, and it hints at something.