With any Hybrid car it is all down to the type of journey and the way you drive. I have owned a CT for 4 years and the mpg varies from 45 - 65 depending on the roads, driving conditions and my mood.
Yesterday in my CT, i drove to see my daughter who lives 75 miles away. The journey is mainly motorway and 'A' roads. I managed 55 mpg.
I do a regular trip to another town about 30 miles away which is all 'A' and 'B' roads and can get up to 65 mpg as my speed rarely goes above 50 mph. The best speed for a hubrid is in the 30-45 range, which means the battery takes over more.
When I just doing local trips to shops, or taking the wife to work etc the mpg is down to 45, this is because the engine has hardly warmed up before it is switched off again.
If I am in a hurry I drive more aggressively and my mpg drops 10% but if I am really careful and drive so that I am keeping the hybrid on low revs it can go up by 10%.
Overall in winter my average is 45 but in summer 55 roughly.
These are figures for the CT I currently own. When I get my NX I will report back.