I would recommend them. I travelled down from Cairns to Byron Bay with them and made some great friends along route. They do organise evening drinks (which help people meet each other) and point out things along route.
For me the most convenient part of using Oz Experience is that I had only 3 weeks down the east coast and it made it easier being able to book accommodation on the bus or arrange my Whitesundays tour as they had all the options to hand and you were 'guaranteed' a spot on one of the sail boats.
I also used the Greyhound when travelling up the centre with a friend and it is comfortable way to get from A to B. And if you ask at the Rest Stops a lot of the bus drivers are happy to answer any questions and give their opinions of their surroundings

If you have the time and are looking at saving money then I would compare prices of passes (I think Greyhound also do a East Coast Pass) as you can always make good friends whereever you choose to stay.