I do not know storealex, I did some tests with Cavalry charging permanently, always head on, into Hoplites.
I tried it with Standard Cav and Hoplites in this thread, and I tried it later on with Spartans and Sacred Band Cavalry.
Spartans are cool Infantry vs. Infantry, but I doubt their usefulness! All Cavalry works surprisingly well, but it should not.
Advantages are high speed compared to slow speed and the surprinsingly HIGH vulnerability of all those units against arrows - even the Testudo does not help that much, as one would suppose.
Come one, hitting phalanx troops in the flank, rear or sides or pepper them to death with arrows is not really a problem.
As you can see, I favor Cavalry and its ultra-strong charge attacks. I wonder what will happen if I will play Parthia (Cataphracts, Horse Archers...) or the Seleucids with their incredible range of quality troops.
Silver Shield Pikemen are among them, too. One of the best units for slow AI bashing. Just want to tell that winning a battle with Cavalry is usually 5 times faster.
Detailed discussion should occur at
www.totalwar.org - I am not playing Rome right now, my Carthage Campaign has come to the point of more micromanagement then fun. I wish the 3d battles had - the higher speed is not even the issue - more tactical depth.
I am sure you have already had dozens of 10000000 : 1 kill ratio wins on medium or hard. I play on hard, very hard is a bit like Sid, the AI gets obscene boni, but players have shown that Cavalry is still good enough to break their morale and rout even Romans.