Jaja,
Don't have any technical info to hand but heard a presentation on this and other 'improvements' at a symposium recently.
Auto tilt is exactly what it says...an automatic tilt function for the radar beam. The system interfaces with EGPWS terrain data to always set the tilt so that ground returns will be just available depending on what range you have set on the ND. In this way as one reduces range on the ND approaching a storm cell, for example, the tilt will automatically be lowered. In this way ground clutter suppression is not required since it can not be seen.
This has been introduced because incidents in the past have shown that users are not scanning down as they get closer to see a true picture of what is ahead of them.
Personally I like having control of the tilt myself and tho I haven't had a chance to use one of these new sets yet, it once again seems like automation trying to do the job. Apparently both AI and Boeing are much in favour!