AVOID AT ALL COST.
I know you got off the plane and you're tired but excited and just want to get to your hotel asap. They know the game and placed their ticket booth and salespeople right at the airport exit. And most likely, if you haven't done any research beforehand, like me, you'd fall into their trap and purchase their shuttle service. Now this is more deceptive than any blackjack game.
Now what do you get? Super long wait (at least 45 mins) to the hotel, and 45 mins late back to the airport. Fine I don't mind being a little late to the hotel but I DO MIND NOT CATCHING MY FLIGHT! I called and they put me on hold for 20 mins and told me to wait 7 more mins or else they'd send a rescue bus over. Hello?! You should send a limo to rescue me from the Bellagio RIGHT NOW! I saw the fountain show three times during my wait!!
Overall, just do Bell Trans (haven't tried but during my wait at the hotel I saw two arrived) or get a cab. Save your money, time and every..and the potential to miss your flight.