This issue is a living tracker for known caveats & breaking changes of v2 compatible mode to facilitate visibility:
The information is updated as KFP 1.7.0

Breaking changes:

• https://www.kubeflow.org/docs/components/pipelines/sdk/v2/v2-compatibility/#building-pipelines-using-the-kubeflow-pipelines-sdk-v2
• command must be specified in Kubeflow Pipelines component specification.
• [v2compat] cannot override container image as parameters #5834
• v2 compiler has data passing limitations #5711
• v2 compatible mode will require KFP backend 1.7.0+, but v1 mode does not have any prerequisites on KFP backend version.

Known caveats:

• Pipelines do not run on the full Kubeflow distributions with Multi-User Kubeflow Pipelines. #5680
• [v2compat] pipeline with output name containing space cannot compile #5831
• [Launcher] support non-root containers in v2 compatible mode #5673
• [v2compat] v1 metrics support #6132
• [sdk] V2_COMPATIBLE mode don't work with parameter input for setting resources.  #5835
• v2 compatible mode and v1 mode have different perf / scalability characteristics, which we haven't verified in large scale.
• Because there aren't enough usage, it's very likely there are more changes we haven't found/thought of.
• When consuming an input artifact by URI, its file content is still downloaded to the container regardless. #5671
• [sdk] VolumeOp support for sdk v2 #6429

Fixed caveats:

• [backend] v2compat - recurring runs fail with "Failed to create component launcher: Invalid launcher options: must specify RunID" #6293
• Pipelines using v1 mlpipeline-ui-metadata visualization do not compile. #5666
• UI integration is implemented.
• Caching is work-in-progress. #5667