A well played Bard is awesome, in RP encounters. Skill wise he's second only to the Rogue, and because his prime attribute is Charisma, he can easily become the master of Diplomacy, Bluff, Gather Information, etc.
In combat he'll be second string at best.
There area couple of spells needed to get him up to that second string status, however. One is Bladeweave.
It's a 2nd level Bard spell, swift action cast, that lets him make touch attacks each round, in addition to his normal melee attack. if the touch succeeds, the opponent has to make a Will save or be Dazed for the round. That means they essentially lose the round. No attacks, no actions.
In essence, it lets a Bard tie up a melee monster, one round at a time, and maybe nickel and dime the thing on hit points while waiting for a real fighter to come up and actually kill the thing.
Another is Alter Self. It lets him change into something that's effective in combat. Troglodyte gets +6 Natural Armor, for example. Avariel (Winged Elf) gets to fly (very slowly). Sea Elf or Sahaguin gets gills and underwater movement.
The spell limits you to creatures of your own type, such as Humanoid, but if your Bard happens to be a Half Dragon it can get nasty!
Illusions, when well planned and played, can be powerful. Our Bard likes to throw a Silent Image of a cloud of fog around us. He'll advise us that it's an illusion, so we get the Save (with a +4). Enemies don't get a Save at all unless they have reason to think it isn't really an Obscuring Mist. So they're messed up by it and we aren't.
Enthrall can be a powerful spell in a social situation, capable of holding an angry mob immobile, or gathering and holding an audience when you really need a traffic jam.
Beyond things like this, he's there as a buffing character. He makes others more effective in combat, but will never be really effective alone. The larger the party, the more effective his buffs become.
Typical PC party of 4? Leave the Bard at home. Party of 6 or more? Bards become worthwhile.