I played GTA4 on the 360 and now I'm playing RDR on the PS3. I can't really see what they are complaining about. The RDR cut scenes to me look worse than the in-game play. And it was that way on the 360 with GTA4. But I'm not a graphics whore. I mainly care about the game-play.
I've played about twelve hours now. Half on my slim PS3 on a 28" Hanns-G 1080p LCD and the rest of the time was spent play on the older fat 80gb PS3 using a 50" Panasonic 1080p Plasma. It looks good on both but the plasma takes the prize. Runs smooth and looks fine on both my PS3s.
My friend plans on getting a second copy so he can play the Co-Op and multi-player with his son on the 360. I'm curious to see what he says.
As far as the horse running speed... it just takes a tap of the button to spur the horse every three or four seconds to keep it at max speeds. I think the horse riding is very well done. In fact at times if you're going to save some of those strangers in trouble ride up on them at full speed with your weapon drawn hit Dead Eye and pick out your targets.
My biggest complaint is the Dead Eye version that picks the shot for you. Once it starts pick the shots and placing the Xs on it's own I'm finding it less enjoyable. Is there a way to shut off the middle version of Dead Eye when it starts picking your shots? I hear there are three versions of Dead Eye in the game.