One of the key things for me is Compass’ typographic functions and mixins. Do you not find these useful to work with when establishing a vertical rhythm?
Although I could switch away from using Compass I haven’t really seen any negative side effects to using it in contrast to just plain Sass but lots of positives in terms of already having a pool of useful and well documented functions, mixins, and utilities. If you end up creating several of those yourself I don’t really see the advantage and it just means that others picking up the projects (including your future self) have less documentation and a less familiar base to pick up with.