I can't either - it would be cheaper to take a cab to/from the airport to the Rio than to pay for two shuttles fares and wait. You can essentially get from the airport all the way to downtown for $20 including tip . . . (Note - the last time I did this was January, think there's a new surcharge that would add about $1.50).

Note - there is a thread about tipping the guys with the luggage carts; they can take you to the front of the taxi line if needed. I've never run into an inefficient taxi queue there, though (anything from walk-up to 5 minutes).

On top of that, Harrah's runs a free shuttle to/from the Rio to the Strip, for those who drink too much and are responsible enough not to drive (e.g. my good friends):

http://www.harrahs.com/casinos/harra...formation.html