Finally approved for installation last week.
... just in time for me to leave my job. Whoops.
Well, I've never used the SaaS model, but, having access to the application means I don't have to ask our business partner to make (unbudgeted) changes for us. We also have custom built some tables and their associated WebCentral views, because we're too cheap to purchase the Project Management module.
Most of the customizations I've made while here have been hiding unused fields from the views or adding/making visible other fields we want to start using.
I also tend to get data to report on from the application itself, as I find that faster and more logical than using WebCentral to grab data on the fly (which is probably due to my lack of knowledge, not knocking the interface).
I have saved a few data views for the application, so I can quickly audit our most-used tables, seeing only the problem fields.