Boost:
Charge damage
Horse hitpoints
Speed
Agree.
Nerf:
Maneuverability. A lot. (enough so they can't stop or avoid a correctly timed and drawn pike when at near full speed.)
...
This is not realistic for anyone who ever rode a horse.
It IS realistic for anyone who REALLY knows to ride, and not just thinks he can. That is abut 1 out of 1000 so called "horsemen".
Of course velocity counts as you can't suddenly turn around at very high speed but horses can still maneuver very well. High precision is also possible but requires a rider who is good not only in riding but in dressage (I mean the classical art, NOT the laughable "sport") as well.
However it is likely that in the middle ages most knights did not have much more clue about true riding art than sport rider today so in this light it makes sense that they could not achieve such perfection. We know some riding masters from later ages in Europe (Like for example Antoine de Pluvinel) but they taught only a very thin chosen "VIPs" like kings and princes, the ordinary knight did not have too much chance to access such knowledge. One notable master too from later ages is William Cavendish, First Duke of Newcastle Upon-Tyne who was not only one of the greatest warlords but also the greatest riding masters of his time - but this is another topic.
If you are by the way interested in early medieval combat, read King Duarte's manual titled Bem Cavalgar Toda Sela - though it is in Portuguese and sadly I do not know of any accessible English translation so I could not read it myself yet.
So, actually I was very happy to see how horse speed and maneuverability had been both raised compared to the first M&B game.
They can insta-stop.
With sliding stop you can stop a horse from full speed in a few seconds btw. It is more lame how they instantly stop and rear in one place when running into something.
* They get shot down from 2-3 hits from an archer or thrower. (But mysteriously survives a pike to the head..)
Well the archer part is realistic. Horses are very sensitive creatures and though they are relatively big and strong, an arrow or a well placed sword blow takes them out just as easily as a human. The pike, well... that should take them out too.
* They dodge arrows like a Ninja.. (This is the worst part, but vital for them of course, so I understand they have to do it)
This is a bit strong...
* They run around in towns and mountains and rooftops and whatnot. Places where a horse would never be preferred.
Rooftops and high cliff walls are unrealistic I agree. But what's your problem with towns?
Pikes would be MORE dangerous to cav, but cav would be MORE dangerous to non-pikemen.
That makes sense I agree.
My few cents...