It'll be interesting to see how the riding mechanics play out because the shots of the trainers atop their steeds were animated really specifically with their hands holding onto the horns like it was a motorcycle - a goatercycle, if you will.
That's it, I just popped in to make that joke
It makes me wonder if each rideable Pokemon will have its own variation of how the trainer holds on to it. That's be a very nice subtle touch. On the other hand, it could just be a feature for that one Pokemon exclusively. Depending on the speed of riding as opposed to walking, skating, or any other modes of transportation, it may be worth catching one just for it.