Oh my biggest complaint with the original is that it embedded itself in my browser and screwed up some things from working right, and would randomly start playing and doing strange things it seemed. This was a number of years ago, so perhaps it's smoother now.
My second biggest issue is resources. My approach to PC operations is that programs should NOT auto load when I boot up my machine and should NOT be resident in memory unless specifically called upon. Resources are limited, why waste them on something I'm not using? I see now that there's a little QuickTime icon on the bottom of my PC screen when I boot up - which oft means such is preloaded into memory. This slows down my computer and slow computers make the Panda sad. If I can play the media via Windows Media player which I have already, why have two?
Nonetheless, if removing quicktime screws up my iTunes functionality, and iTunes really is all that as folks are saying, perhaps I should give it a shot for a few days ;)