These are the issues that are remaining that we (the a11y team) want fixed prior to merge: https://github.com/WordPress/gutenberg/issues?q=is%3Aopen+is...

When these issues were added to the merge proposal, they were what were left for 2.0 level A. But accessibility regressions have gotten introduced many times now while other developers are working on things from other merge proposals. We were doing some tests with users of various assistive technologies, and these were also the problem areas for them.

Here are the open a11y issues for Gutenberg in general: https://github.com/WordPress/gutenberg/issues?page=1&q=is%3A...

A lot of these are still quite important. The UI is also super confusing, as it's an entirely new type of UI, and it's confusing to figure out where everything is if you can't see it. We are working on some documentation that describes it for assistive-technology users, as it's virtually impossible for them to infer how it works.