Hi, I've been using Okular 18.04 from experimental for a few days now, and quite a lot.
I haven't observe any "regressions". I think it fixes the bug preventing to follow links after "saving" [https:// bugs.kde.org/show_bug.cgi?id=397373]. It might also fix a bug which I had, which caused Okular to crash in conjunction with some mouse selection action in the setting of annotations (I haven't seen any bug report matching that description, but it might be fixed anyway; it was a crash occurring while doing the selections, always, and never happening in any other circumstances; the crash is not reproducible at will though, so it is hard to tell for sure). In conclusion I would say that, as far as I can see, Okular 18.04 is an improvement over 17.12. Thanks, Chris