I've used some SAP-based solutions a few times and the closest experience I can relate it to is late 90s MS Access applications: Everything takes ages. Things that should be easy and quick (e.g. viewing a related record or item) are often difficult and take time. Every form of search function doesn't really work, even with perfect input data. Searching doesn't work if your input is slightly off (e.g. names in wrong order or a typo). Searching takes much longer than makes sense in any sensible manner.

Of course, user's experiences don't matter when selling or supporting a software like this. I don't think it's part of the decision maker's conscious that usability (in the sense of being able to accomplish tasks efficiently) for a software that will be used by a larger part of the corporate workforce might be important not only for the employees using it, but also for the company. These systems can eat up so much work time of employees and create so many issues within a company and in customer or supplier relations...