The user interface was intuitive for our users as they are used to working with other systems like SAP or Oracle - no problems there! They did not find any additional features that were missing in their previous system which made migration much easier than expected (we had some minor issues but these could be solved by simple email communication).
If we would start using this again I think an important thing should improve from my point-of view: Support. We got support tickets only if something went wrong after installation whereas many times things worked out well without us having anything else than just asking via eMail/Chat during office hours. Maybe more customer care available through phone calls?