Like someone else already said, we have Beck and Henne and they don't have to be on the field to develop. Pennington is just a stop gap to get the offense going. We have a lot of talent at positions we need to develop, not just QB. And they're not going to develop if they're led by a QB who can't pick up first downs or get them the ball. Pennington can do that now, and when Beck or Henne develop and are able to take over, they will.
And as for picking up other teams' trash? You gotta get players somewhere. With the draft already passed, moves like this is pretty much the only realistic way we can improve. And I think it's safe to say we did, no matter how minor, we're a better team with Pennington, and we didn't have to give up anything for him, only money form the huge cap space we have, and it's a short contract anyways.