It's generally weak.
Spirited Charge looks weak when you realize what the restrictions are on charging. Plus it's annoying because the battlemats are rarely large enough to enable a mounted PC to use their speed properly. There's lots of extra rules to learn; did you know you could speed up your horse, but that causes you to inflict damage?
Without a feat like Mounted Cohort (which technically doesn't apply to warhorses), the mount is weak. PCs don't want to spend resources on buffing the mount, as they themselves don't want to die. (And your horse isn't always with you.)
Unless you're a fighter, you're probably giving up multiple feats: Mounted Combat, then either Mounted Archery or Ride-By Attack and Spirited Charge. Yet fighters don't have any ability to boost their mount. Paladins do, but not everyone wants a magical intelligent horse and they don't get bonus feats anyway.
Light fighters are weak within the rules, but if you wear heavy armor and carry a shield (like a real knight), you're going to take massive penalties to Ride checks.