We have a client who uses it. They do both reporting and budgeting. They purchased it directly from Prophix. We do not support it.
They are quite happy with it though the integration points have caused challenges from time to time.
We did research on it and compared it to Adaptive Planning, Budget Maestro, and Sage Analytics. At the time they were all fairly equal in price and general functionality from a budgeting perspective. Since our review, Prophix and Adaptive have both added financial reporting components to their offerings through acquisition of other companies. Recent pricing changes of Sage Analytics makes their budgeting solution less expensive now.
Hope that helps.