How powerful does a single-class Bard get?

Hey there,

I just started a new game as a male Eilistraee-Drow bard – she is the Goddess of Song, after all.

After I've already started, I had a look at bard builds and noticed that almost all of them seem to go for multiclassed bards. And while that's not bad of course I do wonder how powerful a bard-only build gets? Or if, in case of the bard, muticlassing is really the way to go?