We used OBI EE for generating OOTB reports and then for preparing few custom dashbaords for our clients as part of project.
The product in terms of installation is simple but heavy and takes some time to generate your first report but when one ic comfortable can play easily with platform and this saves time. We have more than 250+ samples available on reporting, drill downs and graphical interactions which help you to prepare concise reports in one report. The ESSBASE query engine makes it possible to pass complex BI queries to engine in real time and responsive also. Overall nice platform which focuses on web and mobile analytics as well.