Heres my opinion on it.
For the most part, you really shouldn't need anything.
However, it depends heavily on what software (Players) you use, types of files you are dealing with etc.
I agree with previous statement: "None, but if you must Sharks codec"
The only reason I have Sharks Codec pack installed ATM, is due to Video encoding.
I have found the result turn out better when the decoding/re-coding is done via FFDshow.
So thats 1 reason that goes to having the Shark codecs.
As far as Playback:
I use Nero Showtime as my default player as well as WMP12 at times.
So in terms of playback, codecs are really not needed as what WMP12 will not play, Showtime will without issue.
For the most part, WMP12 will play a large majority of the more popular types of files by default quite nicely.
It does have issues with some file types though.
1) MKV files
2) Certain MP4 files. For example if the MP4 has AC3 5.1 audio, you will get a picture but no sound.
In a case like this, codecs can help. (or more likely the haali-gabest splitters) if you want to use only WMP12.
But, if you have a 3rd party player this issue may not be a problem anyway.
For example, Nero Showtime supports MP4 w/AC3 audio, MKV files etc --- and if Im not mistaken VLC does as well.
So the moral of this little story is ... a Codec pack isn't really needed.
For the files that do have issues with WMP12, you could easily play witha 3rd party player.
If you are into serious Video encoding ... well ... codecs may very well be an advantage. At least IMHO.
if you need to play .MKV files.
