Hyperion Planning is useful, and the basic functionalities are easy to use. Forms are easy to build, and the same structure around dimensions is replicated across the webpage/Excel/Reporting studio, which makes it quite easy to build on once the basics are mastered. Smartview, the excel add-in, is really helpful to input larger amounts of data, or to pull through bigger reports.
There is very limited customability. I worked extensively with Financial Reporting Studio, which was incredibly restrictive, which meant I couldn't meet a lot of my clients' needs. For example, I couldn't even change the colour of the borders in the reports!
FRS could also be quite erratic. It frequently crashed, worked very slowly, or changes I made in FRS would not be reflected in the system. There were many instances where one minor change in one bit of the report messed up the entire report, and I'd have to redo it entirely.
There was a lot of functionality that was just lacking, and Oracle's customer support was quite poor. On one occasion, I raised a service request asking for a new function, only to find out the development team had been 'working' on it since 2003.
The interface is not always intuitive for users, so as part of the team implementing it, we often had to answer queries from confused parties (and were confused ourselves). For example, Hyperion Planning only works properly in IE (and sometimes there are issues with different versions of IE), and when the zoom is set to 100%. If it's not, then users might struggle to click on links.
The implementation was to help a big investment bank set up a retail branch in accordance with ringfencing regulations.
From a reporting perspective we moved the bank's reports from Excel -- which required slow manual retrieves -- to Hyperion Planning, so changes in the data were almost immediately reflected in the reports. This simplified the entire reporting process considerably.