Quality of the content - second to none. But more focused on giving value added material that is to be used either in introduction or conclusion.
Coverage - They cover issues in depth which leads to some areas left uncovered. So if you are taking the course, make sure that you also refer to atleast one current affairs magazine to cover the gaps.Cost benefit ratio - It does take significant amount of your time. The amount of gain depends upon your own level of preparation. If you have good basic notes and understanding of various issues of national importance then you will be able to better appreciate the lecture.
If you are still covering the syllabus and lack consolidated notes then you might find it difficult to comprehensively cover everything. In that case, I would rather prefer reading specially designed compilations that provide basic knowledge about current events that happened (except for Vision - information overload :) ) Forum's course will give you value added material for the known issues so that you can impress the examiner. But they expect you to already have the base.
If you take forum's course without a solid base, what is likely to happen is that you might end up scoring 60% in 5 questions but below average score (<40%) in other 10 questions.
However, as we have discussed the goal should be to score 50% in ~15 questions. You do the math, which path will lead to a better score.
Thus, cover your back first and then go for the kill. Forumias course will enable you to get high scores, no doubt about that. Make sure if you take the course, you don't lose sight of the low hanging fruits.
~ UPSC CSE Toppers