You really want to pick up suggestion. It's a pretty cool ability. If you've got a good enough charisma modifier, you're looking at a DC 20 or more Will save (the weak suit of many things that rhyme with "wig stupid blighter") or they do what you've told them. That's with only 6 levels of bard, and you can do that 6 times per day. You also, I think, still get access to 9th level maneuvers.
In fact, that's pretty much the only thing I'd miss if I prestige classed out of bard. That and especially mass suggestion. It takes a while to get going, but once you get your perform modifier up it's basically free leadership.