I did this trip in September 2012. I've put on the forum a comprehensive review.
No offence to others but don't listen to those who have not been. I have and it was just excellent from start to finish. Read my review - I couldn't praise it enough.
The day travelling through the desert was an adventure. They were building a new very good concrete road through the desert when i was there that doesn't melt in the sun. A couple of years on I guess a lot more of it will have been improved. The bus has a loo :-)
Do it.