Actually, recess appointments are not illegal, and therefore don't constitute an impeachable offense based on a violation of the law. The way Dubya uses them however, violates the intent of the procedure.

Dubya has used recess appointments before (most notably, Bolton), and it is just another way of showing his scorn and contempt for the Constitution and the Congress. He truly believes that he is above the will of both the Congress, and the People.

For the entire time that it has been in office, this administration has operated on loopholes and questionable ethics, to include: recess appointments, signing statements, legal opinions by a politically biased Justice Department, and purposely directed misinformation (commonly known as propaganda: half-truths, and outright lies).