It depends on what you want to do. The stock CMS fence offset from the router bit is set with a bump and tap until you get it where you want. The incra is zero'd out to the bit, then just use the scales. As you lock it down, the mechanism engages the threaded rod and it locks perfectly and exactly where you want. If you need to fine tune it the micro adjust will move in thousandth's of an inch (with a positive detent so you're not guessing). If you screw up a piece and need to come back and redo it, no problem, that fence system will position the fence exactly where you want it, time after time. There are multiple slots on top for scales, so you can have one scale zero'd out for one operation and other scale for another operation. If you want to plow an ~18mm dado with a 1/2" bit, get your calipers out and measure the panel thickness, measure your bit width exactly, and add 3 thousandths for clearance and do the math to figure out how much that fence needs to move to get your desired result. It will be perfect. The fence halves can be offset for jointing in fine increments as well. It uses two tapered wedges with increments on them, so less elegant than the micro adjust above, but still very accurate.
I'm sure there are other ways to accomplish everything above in a more accurate way with the factory fence, but the incra makes it easy.
They provide templates that slide into the scale slots on the top. These templates allow you to make machine cut dovetails and finger joints with precision. You do have to go through a few test cuts with scrap to get the bit height right and zero the fence to the bit, but once you've done that, just follow the cut marks on the template.