This past July, I drove from Big Red out a couple of km past Eyre Creek and back to Birdsville, admittedly without the trailer on, and had no problems. The only previous sand driving experience I'd had was on Stockton Beach, and that was only limited.
I really enjoyed the dunes and could have kept going and going all the way to Mt Dare had we not had the dog with with us. Hubby very nearly didn't get the driver's seat back
I actually found the Western side to be more cut up than the Eastern, but it obviously changes regularly dependent on traffic and weather. Even the difference in Big Red over the two weeks between when our friends went and when we went was noticeable.
Our travelling companions this year towed a camper East to West across the Simpson Desert and didn't get stuck once, despite the heavy downpourwhilst out in the desert and the access being closed behind them(lots of unhappy campers at Dalhousie who weren't allowed to cross
).
He was in a 200 series Cruiser towing a Kimberley Kamper with another single vehicle.
Unfortunately, we had to drive around and meet them at Oodnadatta, so would love to go back one day to fully cross the Simpson.
I don't think 2014 will be our year though, but good luck to all you lucky buggers who are planning on doing it
Cheers
Karen