Triggered by the question why should I not use the koma script classes results practically necessarily a consequence question: What packages are incompatible with KOMA-Script?
KOMA-Script offers scrhack (see documentation in KOMA-Script manual, chapter 16) to fix certain well-known problems with the packages:
hyperref(Thehyperrefhack inscrhackis only for very, very old versions ofhyperrefand does nothing for the currenthyperrefrelease),float,floatrow,setspace(in older versions corrections took place, in the current version no corrections are needed),listingsandnomencl: The current version (year 2017) ofscrhackprovides a hack fornomenclthat not only increasesnomencl's compatibility with KOMA-Script classes but also provides several new features (all from packagetocbasic) fornomencl, e.g., automatic running heads or numbered heading. AFAIK this can be used not only in combination with KOMA-Script classes but also in combination with standard classes.
In the question incompatibilities between babelfrench and koma script classes? special problems of \usepackage[french][babel] are reported.
Which packages do you know having problems with KOMA-Script?
geometryresets the fromtypepagecalculated margins if you don't use the optionpass(forshowframe). – Qrrbrbirlbel Sep 19 '12 at 18:49setspaceis also supprted byscrhack– Johannes_B Aug 09 '15 at 12:04scrhackdocs). Is KOMAScript broken with no workaround with hyperref (as I thought from the question), or has the problem been fixed for good? – Blaisorblade Jul 11 '17 at 16:58hyperrefare no corections neccessary. The maintainer ofhyperrefis very active ... – Mensch Jul 15 '17 at 17:39setspacepackage is not, or not fully, compatible with the Koma-Script document classes? The user guide mentions thesetspacepackage several times -- and not in a cautionary sense. – Mico May 02 '20 at 08:39