Do you mean M-Drive transmission? I have no experience personally, but this year the local carrier (road trains only) got their first superliner with M-drive and the MP10. A mate who drives there, told me that it's a great truck, and "everyone wants to drive it". All the other trucks have 18 speed manual Roadrangers, so you might think that there would be some resistance towards an auto transmission, but this is not the case. Apparently there are going to be a few more superliners in their fleet next year.
I read somewhere, that 95% of the bigger new Macks in Australia are ordered with the M-drive. I guess time will tell on their reliability, but the driveability is certainly good.