Here's my walkthrough on swapping a 2011 STI wheel into your 05-07 Legacy or Outback. In my opinion it makes the interior look new again. Renew your leather, get some steering wheel audio controls, or just get the nice red-stitch look without spending $600 on a DAMD wheel. Credit to MasAyinde for the cruise control wiring.
If you're going from an 05-07 you need an airbag for the new wheel (or at the minimum an airbag cover without the igniter).