Random has been very helpful on SU and he would be one of my first choices for moderator additions. ~quack would also get my approval. There are a few others that have proved themselves to be very helpful on SU, but those are the top two I have noticed lately.
Core to this approval is not only flagging and editing questions, it is helping users understand why things happen or point them to the information they need. When certain questions get closed or other various site "features", these guys have helped people in a positive way.
On top of that, they have been very helpful finding duplicates, helping identify questions that can be merged, and pointing out places where moderator actions are needed. They have helped make moderator tasks much easier. Random was also very helpful when the SU rules were tightened in finding older questions and content that needed to be cleaned up or closed.
He has my endorsement. If people would rather vote for a new mod, I say let the people decide. From the response here, it sounds like random would be a top choice.
This message is Troggy approved and keep flagging away!