Ask HN: Code libraries for ETL?

Have been looking at a few Python libraries for ETL, namely petl, pygrametl, and bubbles. Wondering if anyone can chime in on the stability and usefulness of those or others (Python is not a hard requirement). Experiments where they passed or failed, success stories. Not as interested in cases where PDI/KETL transforms (or the like) were called from scripts. That is a different beast all together, especially from a debugging standpoint. (reposted from /r/ETL)