I would say more bug fixes than new embellishments.
There are many less access violations, and I have pointed out a few more, which they acknowledges reproducing, and will be included in next releases(s).
Since I use ERA Hotfix so often, I don't really remember what is new. I seem to recall a press release of what was covered, but couldn't locate that release.
I would think that Sierra would attempt to implement at least several new features or feature extensions that I have suggested, and I have high hopes for same.
So time will tell. The program is definitely more stable, much welcome relief.
Their Tech Support has been exemplary in verifying any problems I have reported, or, even better, showing me ways to perform several common tasks.
I would say that I am very pleased with Sierra, in the Hotfix program. Personally, we have 3 copies of ERA 17 on hand at this location, and have purchased many, many of the add-on components and features.
One of the best features is to get vectors from CorelDraw, and this feature is working with all CD 2017, 2018, and the much-hated CD 2019.
SVG import also works very well, to bring in vectors from AI, Inkscape, CD, and other SVG-generator applications.
I realize this doesn't actually directly address your question, but it does provide a little information from an actual user who handles ERA daily.
I do expect a long future with Sierra Hotfix, and doubt it will be yanked out, like some Arizona graphics arts suppliers.
By the way, we use ERA for both stones and spangles, having both kinds of machines.