Hi Sarahnfred - I only managed the Yangon/Bagan segment as I had to terminate my trip midway in Mandalay due to a incident. It's a very comfortable journey. I reached the bus station and paid cash. They took my luggage and wrap in a plastic bag, tag before storing it in the bus luggage compartment. Bus departed on time and was provided a bottle of drink and a snack box. Very Comfortable and clean luxurious leather seat - seat arrangement is single seat at one side and 2 seat at another side. The driver drove at a very safe speed (I watched many other buses 'flying' past us) and there's a change of driver at midway (rest time for driver) Also a stop at midway for toilet and supper break (at Feel eating place) - the place and toilet is very clean too.
I will be going back to Myanmar again and do my Yangon/Taunggyi (Inle)/Yangon in Feb this year, Have emailed JJ bus to book my bus ticket and they have replied asking me to email again nearer the date.