No, I have not, but from previous train experience, that will be a 30+ hours on a train, about 3,100 Kms, 20 stops or so, and I will not settle for anything less than a soft sleeper.  And within a soft sleeper, I will choose a lower bunk, it gives you more room and flexibility. 

For further information, please check : 
http://www.travelchinaguide.com/china-trains/views.asp?tid=T69

and :
http://www.chinatraveldepot.com/ChinaTrains/china-train-T69.html

This is not a direct answer, but kinda related. Be extra careful to book as far ahead as you possibly can (I know this can be tough). Lots of colleagues were grumpy last week because they missed out on train tickets home; seems the trains are particularly busy at the moment because the airport's been shut so often this winter.

yes i took the  Tt69 to Urumqi in 2006 it was a great experience over 40 hours but plenty of stops the soft sleeper was good slept like a baby got off the train at each stop walked around stretched buy some fresh food from the food vendor back on the train after 10 minutes .safe and secure plenty of police on board no hassles at all