I play/DM several living campaigns, and mounted combat is... interesting.
The players of characters with mounted feats often complain that too many modules don't allow them to use their mounts.
I've seen a player with a high-level mounted archer type, who is quite deadly - gets to where he wants to be on the field quickly, etc.
I have a 4th level character with ride and handle animal, and he owns a lance, but has none of the feats, so I'm happy to get the chance to use it, but don't care if it doesn't happen.
If you are playing a mounted marshall I hope your DM lets you use your feats. But it also depends on the other character's specialities.
BTW, if you read the D&D faq it has recently included some rulings that made Ride-by attack almost useless, as you cannot overrun, must continue in a straight line, etc, which basically means that unless you down your opponent, you can't use the ride-by.
Another point, if you are interested in doing more mounted combat in your game(s), I would suggest you read Skip Williams "Rules of the Game" articles on mounted combat - it's a pretty good overview of the whole mounted combat situation.
Mass Fly on mounted PCs = fun, as they can then separate into pairs of rider and mount
Duncan