It's absolutely worth the cost of the option. The resolution is very good, the staging is very good, the bass response is fairly legit, and the frequency response is reasonable. You'd have to spend far more to get the same overall quality. I'd say the only major negative is it doesn't play crazy loud, but even at max volume there's no noticeable distortion, so I'm assuming the volume limiting is done intentionally.
Versus the base stereo, every aspect is better, but what really shines is the significantly lower bass distortion, actual high frequency response [thanks to the added tweeters], better resolution everywhere, and a much better soundstage thanks to the center mid/tweet. If you like music at all the h/k option is a no-brainer, unless you were planning on dropping big coin on a fully developed aftermarket setup.