We booked airfare back in may for travel from LEX to Aruba for Jan 26-Feb5 via US Air. We are going for our 20th wedding anniversary so the dates are important. Airfare on other carriers is at least double what we paid. Would it be wise to book on another airline or just wait and see what happens?
I know others are supposed to honor the tickets on a stand-by basis, but I don't want to take a chance of not going when scheduled.

To be quite honest if you have reservations already made I would stick with your current plan, and not worry about it. While something happening to US between now and your trip is a possibility, I would only look at it from the perspective of being READY to execute alternative plans very quickly in the event that happens. You do not know the reaction, or hoops you may have to jump through, at the other airlines when this actually comes to fruition because the law does not stipulate the method by which they have to honor your tickets. It provides that they must at a minimum offer seats on a space available basis at a maximum cost of $25 each way, but some airlines may choose to be more proactive to gain your favor. Therefore if you act quickly, you may be one of the first able to procure available seats on alternate airlines. Also, as a worse case scenario be ready to ditch your tickets and pay for passage on an alternate carrier.
I remember once coming back from Cayman Islands on AA we were late departing due to mechanical problems. Soon as we landed in Miami I called Marriott and made a Hotel reservation and called AA and rebooked our connection for the next morning. Note that at this point we had definitely missed our connection to WAS and it was the last flight of the day - this is the part of being prepared: know your options in advance. We went up stairs to check on getting vouchers for the Hotel and proceeded to wait in a line of a couple hundred people and discussed our alternatives. We all agreed to ditch the couple hour wait and eat the cost of the hotel ourselves, resulting in a nice dinner and much more enjoyable evening overall. The nice thing was that upon our return home, I wrote the airline and they sent each of us a $100 voucher for our inconvenience.