The main effect is that it replaces the dock at the bottom, with a highly customizable version of the base android dock.
Along with that it allows for things such as adjusting how many collumns of apps show in the drawer, do the app icons display the label text or not, things like that.
with the ability to drop in graphics for differant dock backgrounds, and swap out some icons, it can lead to a nicely custom look for your phone, as well as being impressively light on resources.