Script and Ruby cards are broken for now (in some cases?), as a result of the inclusion refactoring. They'll be fixed when we add nuanced control of content rendering.
refactor inclusion processing also resulted in headers in inclusions showing up in tables of contents, which we may want from content/titled/open inclusions, but the ones from closed view inclusions were really messing up ToCs. The solution for now was to default ToCs to being off everywhere (by changing *all+*table of contents to 0), but you may have custom table of contents settings that you need to adjust. We're still designing a better solution - see have ToCs reflect only some headers in inclusions.
Slash-star as markup to generate HTML code /code tags has been removed as a feature (in order to continue allowing slash-star to be used to make comments on *css as we switch to a simple url for text pages like css). You can get add "pre" to the Format menu of the editing toolbar's by adding it to theme_advanced_blockformats on *tinyMCE (we've done it here on wagn.org so you can look at that link to see how it's done). "Code" doesn't work, but it's probably less desirable anyway.
When you run migrations for this release we will adjust permissions for *css so that it is readable by Anyone. You can change that if you like, but it is necessary for that CSS to be applied for people who are not signed in. (This is also a consequence of us moving CSS from style tags on every page to a separate http request which accesses *css - which is why we made a simple url for text pages like css.)
If you have cards with Unicode characters in their names, you may see them appear in Recent Changes occasionally as part of migrate existing card keys for Unicode fix. (You shouldn't have to do anything about it, this note is just to point you to why it's happening.)
Table of contents now picks up h1 and h2 tags inside inclusions and generated by titled view. This can make for a messy table of contents in many cases, so we defaulted them to off on all cards. We'll improve on this when we refactor table of contents.