I have upgraded to Typo 5.4.1. Partly because of security issues, partly because of new features and improvements.
It took me a while, mostly because of stupid Ruby deployment nonsense that makes me even more tired of Ruby as a language for production usage, than I already was. Oh well.
One of the most important new features for me in this release was the article preview, which doesn't seem to work. Or maybe it does, but then support for writing blog posts in Textile seems like it was dropped. Suggestions for other blogging platforms that aren't a pain to upgrade because of the language dependencies, supports writing in some wiki-like syntax (e.g. Textile or Markdown) and generally works well are very welcome.
It seems that everything is in place and working now, but if you see anything misbehaving, please give me a shout and I'll try to fix.