I believe these questions are firmly outside of what the Stack Overflow / Stack Exchange system was intended to support. II also believe that one of the most important features of the sites is that we don't have to shut down every question that falls outside of the rules. The filter is flexible and flawed by design, so that the community can easily to choose to make exceptions.
For the Hidden Features questions, I think it depends greatly on the quality of the question as asked and the quality of the answers, and so we should evaluate these on a case by case basis. II think that will be okay, as long as we do have a place like this we can point to when we close questions that clearly indicates they are outside of what is normally allowed.
Personally, I learned a lot from these questions. II started on this site in August of 2008 primarily as a winforms vbWindows Forms VB.netNET programmer (and not a very good one). WithinWithin a few months I held the top ASP.NetNET spot (recently yielded to Jon Skeet), became one of the top C# contributors, and for a short time was #5 overall by reputation. AA lot of it was due to the amount of time I was able to put in to Stack Overflow just answering questions during that period, but that's not the whole story. TheThe other side is the amount of new knowledge and skill I took away from Stack Overflow, just by using the site. I experienced incredible growth as a programmer during that period, and Hidden Features -like questions, as well as some other more general questions that today would be quickly closed, were instrumental in how I gained the depth of knowledge needed to contribute at that level. I would be loathe to deprive others of the same gems.