We're about to finalise our mortgage in the next few weeks and don't think we'll be fixing.
If we were to fix on the number of years we wanted (5 years) it's approx 2% higher than variable at the moment. As MD pointed out, you also can't have a redraw facility or an offset account (most banks anyway) and I figure the amount of interest that will be taken down due to having an offset account will outweigh the benefits of fixing.