We are approaching the point at which the current version of Git master is ready for release as Poly/ML 5.7.1. Version 5.7 introduced a number of significant changes and it has taken quite a bit of work since then to fix various bugs and sort out performance issues. I've been working with Makarius on dealing with those that affect Isabelle and we now seem to have dealt with everything. I'd like to ask everyone to try out the current version and let me know if there is anything that would stand in the way of a release.
David