I am not kidding at all. Its barely faster than running, gets stuck on tons of tiny geometry, and while it has some small advantages like an initial reduced agro radius, if I am not racing to a world boss, I mostly don't bother with it. It sucks. As Chris mentioned there is a stuttering issue. For me, after it hits something in the geometry, it seems mine will trot at times and not run under any circumstances for a while; Its like WTF WHY IS MY HORSE WALKING. That sucks particularly when its mobs, who can definitely knock you off your mount.
It's just a shit implementation of a mount. Maybe my Barbarian needs to lay off the barbells and twinkies. Again, its my opinion, your experience may differ.