A major challenge is that "IBM Power Apache Spark" is not consistently reviewed as a standalone product on major review platforms; many reviews address Apache Spark generally or managed Spark platforms.
G2 (Apache Spark — general product, not IBM-specific) includes mixed sentiment about Spark overall: positive notes on performance for large datasets and multi-paradigm support (batch, streaming, SQL, ML); negative notes on operational difficulty, tuning requirements, debugging complexity, streaming semantics, and version compatibility issues. These general Spark experiences are relevant to any Spark deployment, including Spark-on-Power.
PeerSpot and other comparison pages host content comparing Apache Spark against IBM Spectrum Computing; those pages are directional but not specific to Spark-on-Power.