I have been using KMplayer for 2/3 years, but it seems like forever - it is a dear old friend. Easily the best multimedia player for so many varieties of audio and video. When other players (yes, I do use others occassionally!) don't cut the mustard, I just drop it into KMplayer and KNOW that it will work. When playing music and relaxing I switch the 'Milkdrop' visualization on which is by far the best I have ever seen; no drugs needed when that's displaying.
I said it was SO LOUD - and I mean it; when playing DVDs on other players with the volume fully up, the sound level is pitifully low. With KMplayer you can get so much more volume out of DVDs - and no distortion. All the tweaking gadgets work well and there are a host of those.
I wouldn't leave home without - KMplayer of course! It's playing there in the background as I write this.
Best:
Loud volume. Tweakability. Good looking. Simple. Small size.
Worst:
Not worth mentioning.