I should add that at least in English, the documentation for KOMA is considerably more sparse than most similarly-scoped LaTeX packages or classes on CTAN. (Compare it, for an extreme example, to TikZ, which has great documentation, with specific compilable examples available for just about anything one can imagine wanting to do, both in the manual, and on the web.)
If one is newer to LaTeX, one is therefore much more likely to struggle, more often and longer, with KOMA than one would with the standard classes, where a quick web search will provide an answer to almost any beginner's question. With KOMA, you have to rely pretty heavily on the poorly translated manual, because there isn't as much additional information available on the web. One can usually work out what the translator is trying to say, but there are certainly also parts that are virtually impenetrable.
I didn't have a huge amount of experience with LaTeX when I first tried KOMA, so I learned about all this the hard way when I switched to KOMA part-way through a larger project. I found quite a few things that were trivial to learn about in the standard classes and were theoretically even easier to implement in KOMA. Unfortunately, the documentation assumes a greater level of mastery of LaTeX, which was made worse by the fact that there are parts of the (English) manual that are still today barely comprehensible. Fortunately, I know just enough German to be able to get help in that language. Without that, I likely would have quickly abandoned the class entirely. (Because I did read the German sites and manual, I actually really like KOMA a lot now.)
But as much as I like it, this is really not yet a set of classes that is ready for an English-only LaTeX beginner, or even intermediate, user. The main problem is that the manual assumes you understand more about LaTeX than any similar manual I have encountered, and the (English) writing is sufficiently poor to be hard to understand even when you do know enough LaTeX.
So, a great (perhaps even the best) set of classes for a seasoned LaTeX user, or a native German speaker, but still an unqualified disaster for the English-only novice. Whenever I start a collaborative effort (eg. grant proposal, etc.) with another LaTeX user, and they ask what class I use, we wind up using whatever they like to use. I simply can't honestly recommend the class at this point, since I know that most of my colleagues will feel that learning it isn't worth their time, and will wind up resenting it.
I still like it best for my own work, though.