@JamesSekcienski
We've been using Simple Syllabus for about 2 years now. It's not compulsory, so we usually only have about 100 syllabi in the system each semester, it's usually the new faculty that are using it as we pitch it to them at their orientation and they appreciate that it gathers a lot of the institutional policy language for them, and we have it bring over the data from their previous syllabus each semester so they usually only have to make a few updates.
Overall I'd say it's fairly positive feedback from those that use it
Like @Chris_Hofer said you can setup your template so some parts are editable and others aren't. The tricky thing we've found is if we've left a component editable that also contains some of our standard policy language and need to update that policy language, if they have actually made edits on their individual syllabus, their edits win out over any changes to the template and the new language wouldn't be added to theirs. An example of this is our component for Resources on Mental Health: we have added our on-campus resources to the component but also allowed them to edit it if they choose, so if we ever need to update our info for that component, we need to enable a check box that says "ignore previous content" so it will get those changes, but by doing that we force them to have to manually add their own edits again, and then there's the decision for how long to leave that "ignore previous content" check box enabled: if we do leave it on for too long we keep making them manually make edits and too short they won't get the updated College information. So I would just think carefully about what components you want to allow them to edit.
Another issue we've found is if an instructor cross-lists their sections, they need to change the permissions for the syllabus in Simple to allow the moved sections to be able to view it, though there is a setting in the LTI 1.3 connection that can auto-provision the user to have access to a syllabus if they've accessed it via a Canvas course. They'd probably set you up with the LTI 1.3 from the start so just ask about the auto-provision setting if your instructors like to cross-list.
I will also say their support has been really good the few times I've had to reach out: extremely fast response time! And the ability to quickly download all syllabi from a given semester is very handy.
Hope that helps!
~JOD