Not sure about video, but here's what I know on audio. I really like the way look and feel of the stock HTC app. It is sweet. However, you can't intercept the play controls. This means that while using bluetooth or headphones, you can't skip songs or play/pause. I also found that that the Wigdetoid controls don't work with the stock app.
And so... I moved on (mostly for the headphones and bluetooth). I've tried PowerAmp, WinAmp and Cube (C^3). PowerAmp has a hidious, Palm-like interface. Awesome back in 2002, but well past it's prime. Cube is good and has a really sleek interface, but is kinda buggy. So... I use Winamp. It's not as slick in appearance as HTC or Cube, but it looks way better than PA and everything about it just works.