Most people agree that it is better to install individually... That said, when I re-did my main system a while back I installed the KLite package and have been pretty happy with it. No real problems.
I use the KLite Codec Pack. Never had a problem playing anything. On top of that I also have installed Real Player and Quicktime. Nothing has ever had an issue playing.
The thing is ... the average person doesn't know what they need to get something working, mosin.
Look over that pack @ Defiler and tell me what you think.
I think it's pretty complete and nothing there is gonna hose somebodies box.