For me LingQ generally works quite well for Korean, at least since I got past the initial beginner stage. For the first steps in Korean and other languages which are quite different from the ones I already know, LingQ does not seem to be the best resource anyhow in my opinion. I tend to look for other resources first and then start to use LingQ more regularly.
My biggest challange for Korean in LingQ is currently to figure out the meanings of (some of) the endings. Available translations often only provide the meaning of the verb stem, but not always the complete meaning of the endings. Some useres have already provided very helpful translation and I guess this issue could greatly improve over time with more experienced users adding such explanations.
[Note: I am aware that grammar books also help with this, however it takes time to work through those.]
Korean romanization does more harm than good in my opinion.
My level: Beginner 2 with 4830 known LingQs as per today.