It's pretty good, really. And it is actually a different process for making ice cream that reduces ice crystals (which make ice cream less smooth) and doesn't require adding in extra fat to keep it smooth. So, it's more like no extra fat added.

From Wikipedia:
In 2004, Dreyer's began using a new churning processes called low-temperature extrusion. Unlike traditional churning methods, the ice cream does not need to be frozen once it is done churning. Since this freezing stage produces large ice crystals, which gives the ice cream a grainy texture, manufacturers would add milkfat to counterbalance the grainy texture. As this extra freezing process isn't necessary with low-temperature extrusion, the "slow churned" line of ice cream is labeled as containing 1/3 the calories and 1/2 the fat. Other manufacturers (like Haagen-dazs) have already followed suit and introduced light varieties using low-temperature extrusion.