Only reason I could find for using the Playa was to correct the aspect ratio that a lot of people screw up. Other than that I use Sasami2k for all my video playback. Sasami only lacks Spdif output from what I know... and that most people aren't using yet anyway.
For codecs, I recommend installing the 3.11, then the latest version of 4 (which is entirely different). When installing 4 choose not to have the new one playback the 3.11 or "older" codec videos.